How to print binary tree diagram

Question

How can I print a binary tree in Java so that the output is like      4          2   5    My node   public class Node lt A extends Comparable gt        Node lt A gt  left  right      A data       public Node A data           this data   data

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using map      Map lt Integer String gt  m   new LinkedHashMap lt  gt               tn printNodeWithLvl node l m            for Entry lt Integer  String gt  map  m entrySet                  System out println map getValue               then    method      private  void printNodeWithLvl Node node int l Map lt Integer String gt  m           if node  null               return                 if m containsKey l               m put l  new StringBuilder m get l   append node value  toString            else             m put l  node value                    l          printNodeWithLvl  node left l m         printNodeWithLvl node right l m

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You can use an applet to visualize this very easily  You need to print the following items    Print the nodes as circles with some visible radius   Get the coordinates for each node   The x coordinate can be visualized as the number of nodes visited before the node is visited in its inorder traversal  The y coordinate can be visualized as the depth of the particular node        Print the lines between parent and children   This can be done by maintaining the x and y coordinates of the nodes and the parents of each node in separate lists  For each node except root join each node with its parent by taking the x and y coordinates of both the child and the parent

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I wrote a binary tree printer in Java     Code is on GitHub here   It hasn t been optimized for run time efficiency  but since we re talking about printing in ASCII  I figured it s not going to be used on very large trees   It does have some nice features though    It makes efficient use of space in that a large subtree extends under a smaller one as much as possible  There s a parameter to set the minimum horizontal space between node labels  Node labels are strings of arbitrary length  In addition to a method for printing a single tree  there s a method for printing a list of trees horizontally across the page  with a parameter for page width   using as many rows as necessary  There s an option to print trees with diagonal branches  using slash and backslash characters  or with horizontal branches  using ascii box drawing characters   The latter is more compact and makes tree levels more visually clear  It works    Some demo test programs are included   An example of a randomly generated binary tree  as printed by the program  follows   This illustrates the efficient use of space  with a large right subtree extending under a small left subtree                seven                                                                                                                                                                                                                                                                                                                                                                                                                  five        thirteen                                                                                                                                                                                                                   three    six                                                                                                                                                                   one   four                                                                                                              two                                                                 nine            twenty four                                                                                                                                                                                                            eight   twelve                                                                                                               ten                                                                                                                    eleven                                                                                                                                                                                                                                         eighteen              twenty seven                                                                                                                                                                                                                                                                                                                                                                                                          twenty five   twenty eight                                                                                               twenty six      thirty         fourteen            nineteen                                                                      twenty nine           sixteen           twenty three                                                                                                         twenty two                                                                                                            twenty                                                                                         fifteen    seventeen   twenty one                         An example of printing all five node binary trees  with in-order labels  across the page   one           one         one          one        one       one         one                                                                                         two           two         two          two        two      three       three                                                                                       three         three        four         five       five  two four    two five                                                                                        four          five                three       four          five    four                             three  five                                                    five      four                     four  three                              one          one        one        one       one       one         one        two                                                                                                     four         four       five       five      five      five        five                                                                                            one  three     two five                two        two      three      four        four                              three  five                                                             four    three                   three       four  two four  two        three                               two                                                                        five                             four  three               three    two                              two          two          two        two      three         three         three                                                                                                          one four     one five   one five  one four                    two four   one  three                                                                                                         three       four      two five  one     five  one     five         five  three  five                                                                                             four  three                    two four                       four                                                                                   three      four      four         four         four            four       five                                                                                             two five  one five  one five     two five                                one                                                      three  five     three  five             one four      two      three                                                 two                                      one  three   one             two                                     three  two                                                     three                                                  two         one                                                                                                         four      five      five      five      five       five         five      five        five                                                                                    one       one       one       one        two          two      three       three                                                                                        two      three      four      four                one four  one four    two four                                       one  three                                       four  two four  two      three                   three      two     one                                                      four                                  three               three  two                                                           five      five         five        five          five                                                             four      four         four        four          four                                                             one       one          two        three         three                                                                 two      three                 one           two                            one  three                               three  two                      two       one    The following is an example of the same tree printed 4 different ways  with horizontal spacing of 1 and of 3  and with diagonal and horizontal branches                      27                       -----------                  13          29          -------------    ---         8             23 28  30     -----         -----          4     11      21    26       ---    -      ---            2   5  9 12   18  22 24       -            ---             1 3   6  10  17  19    25                                          7    15    20                     ---                          14  16                                 27                                                                               13    29                                                    28  30                                                                                                                           8             23                                                                 4     11                                 21      26   2   5 9   12                             18  22  24   1   3   6 10                             17  19      25           7                            15      20                                            14  16                                            27                                  -----------------                          13                29               -------------------      -----             8                   23   28    30       ---------           ---------              4         11        21        26          -----      ---      -----                  2     5    9   12   18    22    24         ---                -----                   1   3    6    10   17    19        25                                                             7       15      20                                -----                                      14    16                                             27                                                                                                                                                                   13        29                                                                                                 28    30                                                                                                                                                                                    8                 23                                                                                                                4       11                                         21        26   2   5   9   12                                               24   1   3   6   10    18    22                                       25           7                                      17    19                                                          15        20                                                                                       14    16

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this is one of the simplest version i could implement  i hope it helps you   class Node      def   init   self  data           self data   data         self left   None         self right   None      def add self  data            if data  lt  self data              if self left is None                  self left   Node data              else                  self left add data          if data  gt  self data              if self right is None                  self right   Node data              else                  self right add data       def display self           diff   16         start   50         c                this level     self  start            while this level              next level   list               last line                   for node  d in this level                  line   last line   c  d - len last line     str node data                  print line  end   r                   last line   line                  if node left                      next level append  node left  d - diff                   if node right                      next level append  node right  d   diff                   this level   next level                 diff   max diff  2  2              print   n     if   name         main         from random import randint  choice     values    randint 0  100  for   in range 10       bst   Node choice values       for data in values          bst add data       bst display

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A Scala solution  adapted from Vasya Novikov s answer and specialized for binary trees       An immutable Binary Tree     case class BTree T  value  T  left  Option BTree T    right  Option BTree T            Adapted from  http   stackoverflow com a 8948691 643684      def pretty  String         def work tree  BTree T   prefix  String  isTail  Boolean   String           val  line  bar    if  isTail     --         else    --                 val curr   s   prefix   line   tree value          val rights   tree right match           case None      gt  s   prefix   bar     --             case Some r    gt  work r  s   prefix   bar       false                 val lefts   tree left match           case None      gt  s   prefix   bar     --             case Some l    gt  work l  s   prefix   bar       true                 s   curr  n  rights  n  lefts               work this      true

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A solution in Scala language  analogous to what I wrote in java   case class Node name  String  children  Node          def toTree  String   toTree         mkString   n        private def toTree prefix  String  childrenPrefix  String   Seq String              val firstLine   prefix   this name          val firstChildren   this children dropRight 1  flatMap   child   gt              child toTree childrenPrefix     --     childrenPrefix                                 val lastChild   this children takeRight 1  flatMap   child   gt              child toTree childrenPrefix     --     childrenPrefix                                 firstLine    firstChildren     lastChild            Output example   vasya  --  frosya          --  petya                  --  masha          --  kolya  --  frosya2

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Here is another way to visualize your tree   save the nodes as an xml file and then let your browser show you the hierarchy   class treeNode      int key      treeNode left      treeNode right       public treeNode int key           this key   key          left   right   null             public void printNode StringBuilder output  String dir           output append   lt node key      key      dir      dir      gt             if left    null              left printNode output   l            if right    null              right printNode output   r            output append   lt  node gt              class tree      private treeNode treeRoot       public tree int key           treeRoot   new treeNode key              public void insert int key           insert treeRoot  key              private treeNode insert treeNode root  int key           if root    null               treeNode child   new treeNode key               return child                     if key  lt  root key              root left   insert root left  key           else if key  gt  root key              root right   insert root right  key            return root             public void saveTreeAsXml            StringBuilder strOutput   new StringBuilder            strOutput append   lt  xml version   1 0   encoding   UTF-8    gt             treeRoot printNode strOutput   root            try               PrintWriter writer   new PrintWriter  C  tree xml    UTF-8                writer write strOutput toString                 writer close                      catch  FileNotFoundException e                      catch UnsupportedEncodingException e                        Here is code to test it       tree t   new tree 1       t insert 10       t insert 5       t insert 4       t insert 20       t insert 40       t insert 30       t insert 80       t insert 60       t insert 50        t saveTreeAsXml      And the output looks like this

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I needed to print a binary tree in one of my projects  for that I have prepared a java class TreePrinter  one of the sample output is                                                                                                                                                                                              -   speed       2                                     45       12    Here is the code for class TreePrinter along with class TextNode  For printing any tree you can just create an equivalent tree with TextNode class     import java util ArrayList   public class TreePrinter        public TreePrinter               public static String TreeString TextNode root           ArrayList layers   new ArrayList            ArrayList bottom   new ArrayList             FillBottom bottom  root    DrawEdges root            int height   GetHeight root           for int i   0  i  s length    min   s length                 if  n isEdge  s                     s    n text              if  n isEdge  s                      layers set n depth  s                      StringBuilder sb   new StringBuilder             for int i   0  i  temp   new ArrayList                 for int i   0  i  0  temp get i-1  left   x                  temp add x                              temp get count-1  left   n left              n left depth   temp get count-1  depth 1              n left   temp get 0                DrawEdges temp get count-1  left                     if n right    null               int count   n right x -  n x   n text length     2               ArrayList temp   new ArrayList                 for int i   0  i  0  temp get i-1  right   x                  temp add x                              temp get count-1  right   n right              n right depth   temp get count-1  depth 1              n right   temp get 0                  DrawEdges temp get count-1  right                        private static void FillBottom ArrayList bottom  TextNode n           if n    null  return           FillBottom bottom  n left            if  bottom isEmpty                             int i   bottom size  -1              while bottom get i  isEdge  i--              TextNode last   bottom get i                if  n isEdge  n x   last x   last text length     3                    bottom add n           FillBottom bottom  n right              private static boolean isLeaf TextNode n           return  n left    null    n right    null              private static int GetHeight TextNode n           if n    null  return 0           int l   GetHeight n left           int r   GetHeight n right            return Math max l  r    1            class TextNode       public String text      public TextNode parent  left  right      public boolean isEdge      public int x  depth       public TextNode String text           this text   text          parent   null  left   null  right   null          isEdge   false          x   0  depth   0             Finally here is a test class for printing given sample    public class Test        public static void main String   args           TextNode root   new TextNode               root left   new TextNode                  root left parent   root          root right   new TextNode  -              root right parent   root          root left left   new TextNode  speed      root left left parent   root left          root left right   new TextNode  2         root left right parent   root left          root right left   new TextNode  45        root right left parent   root right          root right right   new TextNode  12       root right right parent   root right           System out println TreePrinter TreeString root

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private StringBuilder prettyPrint Node root  int currentHeight  int totalHeight            StringBuilder sb   new StringBuilder            int spaces   getSpaceCount totalHeight-currentHeight   1           if root    null                  create a  spatial  block and return it             String row   String format      2 spaces 1   s n                      now repeat this row space 1 times             String block   new String new char spaces 1   replace   0   row               return new StringBuilder block                     if currentHeight  totalHeight  return new StringBuilder root data              int slashes   getSlashCount totalHeight-currentHeight  1           sb append String format      spaces 1   s   spaces  s   root data                   sb append   n              now print   and              but make sure that left and right exists         char leftSlash   root left    null                   char rightSlash   root right  null                    int spaceInBetween   1          for int i 0  space   spaces-1  i lt slashes  i    space --  spaceInBetween  2                for int j 0  j lt space  j    sb append                   sb append leftSlash               for int j 0  j lt spaceInBetween  j    sb append                   sb append rightSlash                  for int j 0  j lt space  j    sb append                   sb append   n                        sb append   n               now get string representations of left and right subtrees         StringBuilder leftTree   prettyPrint root left  currentHeight 1  totalHeight           StringBuilder rightTree   prettyPrint root right  currentHeight 1  totalHeight              now line by line print the trees side by side         Scanner leftScanner   new Scanner leftTree toString             Scanner rightScanner   new Scanner rightTree toString             spaceInBetween  1          while leftScanner hasNextLine                  if currentHeight  totalHeight-1                    sb append String format   -2s  2s   leftScanner nextLine    rightScanner nextLine                      sb append   n                    spaceInBetween- 2                                          else                   sb append leftScanner nextLine                     sb append                       sb append rightScanner nextLine     n                                     return sb         private int getSpaceCount int height            return  int   3 Math pow 2  height-2 -1         private int getSlashCount int height            if height  lt   3  return height -1          return  int   3 Math pow 2  height-3 -1           https   github com murtraja java-binary-tree-printer  only works for 1 to 2 digit integers  i was lazy to make it generic

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I ve made an improved algorithm for this  which handles nicely nodes with different size  It prints top-down using lines   package alg   import java util ArrayList  import java util List           Binary tree printer         author MightyPork     public class TreePrinter           Node that can be printed        public interface PrintableNode                   Get left child            PrintableNode getLeft                  Get right child            PrintableNode getRight                  Get text to be printed            String getText                           Print a tree                 param root                   tree root node             public static void print PrintableNode root                List lt List lt String gt  gt  lines   new ArrayList lt List lt String gt  gt              List lt PrintableNode gt  level   new ArrayList lt PrintableNode gt             List lt PrintableNode gt  next   new ArrayList lt PrintableNode gt              level add root           int nn   1           int widest   0           while  nn    0                List lt String gt  line   new ArrayList lt String gt                  nn   0               for  PrintableNode n   level                    if  n    null                        line add null                        next add null                       next add null                     else                       String aa   n getText                        line add aa                       if  aa length    gt  widest  widest   aa length                         next add n getLeft                         next add n getRight                          if  n getLeft      null  nn                        if  n getRight      null  nn                                                 if  widest   2    1  widest                 lines add line                List lt PrintableNode gt  tmp   level              level   next              next   tmp              next clear                       int perpiece   lines get lines size   - 1  size      widest   4           for  int i   0  i  lt  lines size    i                  List lt String gt  line   lines get i               int hpw    int  Math floor perpiece   2f  - 1               if  i  gt  0                    for  int j   0  j  lt  line size    j                              split node                     char c                            if  j   2    1                            if  line get j - 1     null                                c    line get j     null     -                                   else                               if  j  lt  line size    amp  amp  line get j     null  c                                                                            System out print c                           lines and spaces                     if  line get j     null                            for  int k   0  k  lt  perpiece - 1  k                                  System out print                                                       else                            for  int k   0  k  lt  hpw  k                                  System out print j   2    0          -                                                      System out print j   2    0                                       for  int k   0  k  lt  hpw  k                                  System out print j   2    0    -                                                                                            System out println                                  print line of numbers             for  int j   0  j  lt  line size    j                       String f   line get j                   if  f    null  f                       int gap1    int  Math ceil perpiece   2f - f length     2f                   int gap2    int  Math floor perpiece   2f - f length     2f                       a number                 for  int k   0  k  lt  gap1  k                          System out print                                         System out print f                   for  int k   0  k  lt  gap2  k                          System out print                                                   System out println                 perpiece    2                      To use this for your Tree  let your Node class implement PrintableNode   Example output                                            2952 0                                                                   -----------------------------------------------                                          1249 -1                                         5866 0                               -----------------------                         -----------------------                  491 -1                  1572 0                  4786 1                  6190 0             -----                                                 -----             -----------       339 0                                                      5717 0      6061 0      6271 0

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michal kreuzman nice one I will have to say  It was useful  However  the above works only for single digits  if you are going to use more than one digit  the structure is going to get misplaced since you are using spaces and not tabs  As for my later codes I needed more digits than only 2  so I made a program myself  It has some bugs now  again right now I am feeling lazy to correct them but it prints very beautifully and the nodes can take a larger number of digits  The tree is not going to be as the question mentions but it is 270 degrees rotated    public static void printBinaryTree TreeNode root  int level       if root  null           return      printBinaryTree root right  level 1       if level  0           for int i 0 i lt level-1 i                System out print  quot   t quot            System out println  quot  ------- quot  root val             else         System out println root val       printBinaryTree root left  level 1          Place this function with your own specified TreeNode and keep the level initially 0  and enjoy  Here are some of the sample outputs                   -------11          -------10                  -------9  -------8                  -------7          -------6                  -------5 4          -------3  -------2          -------1                            -------10                  -------9          -------8                  -------7  -------6          -------5 4          -------3  -------2          -------1  Only problem is with the extending branches  I will try to solve the problem as soon as possible but till then you can use it too

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Print in Console                                                    500                        700                                             300        200                                   400                                                                                             Simple code    public int getHeight                 if rootNode    null  return -1          return getHeight rootNode              private int getHeight Node node                if node    null  return -1           return Math max getHeight node left   getHeight node right     1             public void printBinaryTree Node rootNode                Queue lt Node gt  rootsQueue   new LinkedList lt Node gt             Queue lt Node gt  levelQueue   new LinkedList lt Node gt             levelQueue add rootNode           int treeHeight   getHeight            int firstNodeGap          int internalNodeGap          int copyinternalNodeGap          while true                        System out println                  internalNodeGap    int  Math pow 2  treeHeight   1  -1                 copyinternalNodeGap   internalNodeGap              firstNodeGap   internalNodeGap 2               boolean levelFirstNode   true               while  levelQueue isEmpty                                  internalNodeGap   copyinternalNodeGap                  Node currNode   levelQueue poll                    if currNode    null                                        if levelFirstNode                                                while firstNodeGap  gt  0                                                        System out format   s                                       firstNodeGap--                                                     levelFirstNode  false                                            else                                               while internalNodeGap gt 0                                                        internalNodeGap--                              System out format   s                                                                               System out format   3d  currNode data                       rootsQueue add currNode                                                --treeHeight               while  rootsQueue isEmpty                                  Node currNode   rootsQueue poll                    if currNode    null                                        levelQueue add currNode left                       levelQueue add currNode right                                                if levelQueue isEmpty    break

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You will need to level order traverse your tree  Choose node length and space length  Get the tree s base width relative to each level which is node length   nodes count   space length   spaces count   Find a relation between branching  spacing  indentation and the calculated base width    Code on GitHub  YoussefRaafatNasry bst-ascii-visualization                                               07                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              03                      11                                                                                                                                                                                                                                                                                                                                                                                              01          05          09          13                                                                                                                                                                      00    02    04    06    08    10    12    14

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This is an interesting question  and I also wrote a project for it   binary-tree-printer  Here are some examples   Print random BST   BTPrinter printRandomBST 100  100                                   38                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 28                               82                                                                                                                                                                                                                                                                                                       5        31                                                                                                                                   30 36                                                                                                                               29  33 37                                                                                                                               32 35               65                   95         1            14                                                                     34                                    94 97     0   2                                                                           12   24                                   93  96 98         3                                                                       9  13 16 25                               84         99         4                                                                   7  10 15 23  26     59             74     83 86                                                                                     6   8  11 22     27 56 60           73 76     85 91                                                                                           20               61       67  75 79     88 92                               40   58                                                 18 21                62   66 72   78 80 87 89                               39 54 57                                                17 19                    64   69  77     81    90                               50 55                                                                         63  68 70                                                                                                                                      71                                         47     53                                                                                                                                   52                                                        42   49                                                                   51                                                        41 43 48                                                                                                                                   46                                                                                                                                   45                                                                                                                                  44        Print tree from leetcode-style level order array      means a path terminator where no node exists below   BTPrinter printTree  1 2 3 4 5     6 7 8 1             2 3 4 5 6 7 8 9 10 11 12 13 14 15              1                                             2   3                                                                4     5                                       6   7 8   1                                                                                                                                         2           3                                                        4     5     6     7                           8   9 10 11 12 13 14 15

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I know you guys all have great solution  I just want to share mine - maybe that is not the best way  but it is perfect for myself   With python and pip on  it is really quite simple  BOOM   On Mac or Ubuntu  mine is mac    open terminal    pip install drawtree  python  enter python console  you can do it in other way from drawtree import draw level order draw level order   2 1 3 0 7 9 1 2   1 0     8 8         7      DONE           2                                         1       3                  0   7   9   1                  2   1   0   8   8                7     Source tracking   Before I saw this post  I went google  binary tree plain text   And I found this https   www reddit com r learnpython comments 3naiq8 draw binary tree in plain text   direct me to this https   github com msbanik drawtree

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See also these answers   In particular it wasn t too difficult to use abego TreeLayout to produce results shown below with the default settings   If you try that tool  note this caveat  It prints children in the order they were added   For a BST where left vs right matters I found this library to be inappropriate without modification   Also  the method to add children simply takes a parent and child node as parameters    So to process a bunch of nodes  you must take the first one separately to create a root    I ended up using this solution above  modifying it to take in the type  lt Node gt  so as to have access to Node s left and right  children

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Adapted from Vasya Novikov s answer to make it more binary  and use a StringBuilder for efficiency  concatenating String objects together in Java is generally inefficient    public StringBuilder toString StringBuilder prefix  boolean isTail  StringBuilder sb        if right  null            right toString new StringBuilder   append prefix  append isTail                      false  sb             sb append prefix  append isTail     --       --    append value toString    append   n        if left  null            left toString new StringBuilder   append prefix  append isTail                      true  sb             return sb      Override public String toString         return this toString new StringBuilder    true  new StringBuilder    toString        Output             -- 7       -- 6            -- 5  -- 4           -- 3      -- 2          -- 1              -- 0

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Print a  large  tree by lines   output example   z  --  c          --  a          --  b  --  d  --  e          --  asdf  --  f   code   public class TreeNode        final String name      final List lt TreeNode gt  children       public TreeNode String name  List lt TreeNode gt  children            this name   name          this children   children             public String toString             StringBuilder buffer   new StringBuilder 50           print buffer                   return buffer toString               private void print StringBuilder buffer  String prefix  String childrenPrefix            buffer append prefix           buffer append name           buffer append   n            for  Iterator lt TreeNode gt  it   children iterator    it hasNext                   TreeNode next   it next                if  it hasNext                      next print buffer  childrenPrefix     --    childrenPrefix                           else                   next print buffer  childrenPrefix     --    childrenPrefix                                              P S  This answer doesn t exactly focus on  binary  trees -- instead  it prints all kinds of trees  Solution is inspired by the  tree  command in linux

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Based on VasyaNovikov answer  Improved with some Java magic  Generics and Functional interface          Print a tree structure in a pretty ASCII fromat      param prefix Currnet previx  Use    in initial call      param node The current node  Pass the root node of your tree in initial call      param getChildrenFunc A   link Function  that returns the children of a given node      param isTail Is node the last of its sibblings  Use true in initial call   This is needed for pretty printing       param  lt T gt  The type of your nodes  Anything that has a toString can be used      private  lt T gt  void printTreeRec String prefix  T node  Function lt T  List lt T gt  gt  getChildrenFunc  boolean isTail        String nodeName   node toString        String nodeConnection   isTail     --       --        log debug prefix   nodeConnection   nodeName       List lt T gt  children   getChildrenFunc apply node       for  int i   0  i  lt  children size    i              String newPrefix   prefix    isTail                              printTreeRec newPrefix  children get i   getChildrenFunc  i    children size  -1             Example initial call   Function lt ChecksumModel  List lt ChecksumModel gt  gt  getChildrenFunc   node - gt  getChildrenOf node  printTreeRec     rootNode  getChildrenFunc  true     Will output something like   -- rootNode      -- childNode1      -- childNode2           -- childNode2 1           -- childNode2 2           -- childNode2 3      -- childNode3      -- childNode4

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Simple python code for Leetcode style tables binary tree visualization posted here  Also cloned here Input   9 5 4 5 null 2 6 2 5 null 8 3 9 2 3 1 1 null 4 5 4 2 2 6 4 null null 1 7 null 5 4 7 null null 7 null 1 5 6 1 null null null null 9 2 null 9 7 2 1 null null null 6 null null null null null null null null null 5 null null 3 null null null 8 null 1 null null 8 null null null null 2 null 8 7   Output

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I found VasyaNovikov s answer very useful for printing a large general tree  and modified it for a binary tree  Code   class TreeNode       Integer data   null      TreeNode left   null      TreeNode right   null       TreeNode Integer data   this data   data        public void print             print     this  false              public void print String prefix  TreeNode n  boolean isLeft            if  n    null                System out println  prefix    isLeft     --        --      n data               print prefix    isLeft                     n left  true               print prefix    isLeft                     n right  false                       Sample output    -- 7      -- 3          -- 1              -- 2          -- 5              -- 4              -- 6      -- 11          -- 9              -- 8              -- 10          -- 13              -- 12              -- 14

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This was the simplest solution for horizontal view  Tried with bunch of examples  Works well for my purpose  Updated from  nitin-k  s answer   public void print String prefix  BTNode n  boolean isLeft        if  n    null            print prefix            n right  false           System out println  prefix      --      n data           print prefix            n left  true             Call   bst print     bst root  false     Solution                             -- 80                      -- 70                 -- 60            -- 50       -- 40  -- 30       -- 20            -- 10

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Here s a very versatile tree printer  Not the best looking  but it handles a lot of cases  Feel free to add slashes if you can figure that out    package com tomac120 NodePrinter   import java util ArrayList  import java util LinkedList  import java util List          Created by elijah on 6 28 16      public class NodePrinter      final private List lt List lt PrintableNodePosition gt  gt  nodesByRow      int maxColumnsLeft   0      int maxColumnsRight   0      int maxTitleLength   0      String sep            int depth   0       public NodePrinter PrintableNode rootNode  int chars per node           this setDepth rootNode 1           nodesByRow   new ArrayList lt  gt  depth           this addNode rootNode  getPrintableNodeInfo   0 0           for  int i   0 i lt chars per node i                   sep                              private void setDepth PrintableNode info  int depth           if  depth  gt  this depth               this depth   depth                    if  info  getLeftChild      null               this setDepth info  getLeftChild   depth 1                     if  info  getRightChild      null               this setDepth info  getRightChild   depth 1                        private void addNode PrintableNodeInfo node  int level  int position           if  position  lt  0  amp  amp  -position  gt  maxColumnsLeft               maxColumnsLeft   -position                    if  position  gt  0  amp  amp  position  gt  maxColumnsRight               maxColumnsRight   position                    if  node getTitleLength    gt  maxTitleLength              maxTitleLength   node getTitleLength                      List lt PrintableNodePosition gt  row   this getRow level           row add new PrintableNodePosition node  level  position            level             int depthToUse   Math min depth 6           int levelToUse   Math min level 6           int offset   depthToUse - levelToUse-1          offset    int  Math pow offset Math log depthToUse  1 4            offset   Math max offset 3             PrintableNodeInfo leftChild   node getLeftChildInfo            PrintableNodeInfo rightChild   node getRightChildInfo            if  leftChild    null               this addNode leftChild level position-offset                     if  rightChild    null               this addNode rightChild level position offset                        private List lt PrintableNodePosition gt  getRow int row           if  row  gt  nodesByRow size   - 1               nodesByRow add new LinkedList lt  gt                        return nodesByRow get row              public void print            int max chars   this maxColumnsLeft maxColumnsRight 1          int level   0          String node format     -  this maxTitleLength  s           for  List lt PrintableNodePosition gt  pos arr   this nodesByRow               String   chars   this getCharactersArray pos arr max chars               String line                   int empty chars   0              for  int i 0 i lt chars length 1 i                     String value i   i  lt  chars length   chars i  null                  if  chars length   1    i    value i    null                       if  empty chars  gt  0                            System out print String format   -    empty chars    s                                                    if  value i    null                           System out print String format node format value i                            empty chars   -1                        else                          empty chars   0                                          else                       empty chars                                                System out print   n                 int depthToUse   Math min 6 depth               int line offset   depthToUse - level              line offset    0 5              line offset   Math max 0 line offset                for  int i 0 i lt line offset i                     System out println                                  level                         private String   getCharactersArray List lt PrintableNodePosition gt  nodes  int max chars           String   positions   new String max chars 1           for  PrintableNodePosition a   nodes               int pos i   maxColumnsLeft   a column              String title i   a nodeInfo getTitleFormatted this maxTitleLength               positions pos i    title i                    return positions            NodeInfo class  package com tomac120 NodePrinter          Created by elijah on 6 28 16      public class PrintableNodeInfo       public enum CLI PRINT COLOR           RESET   u001B 0m            BLACK   u001B 30m            RED   u001B 31m            GREEN   u001B 32m            YELLOW   u001B 33m            BLUE   u001B 34m            PURPLE   u001B 35m            CYAN   u001B 36m            WHITE   u001B 37m             final String value          CLI PRINT COLOR String value               this value   value                      Override         public String toString                 return value                      private final String title      private final PrintableNode leftChild      private final PrintableNode rightChild      private final CLI PRINT COLOR textColor       public PrintableNodeInfo String title  PrintableNode leftChild  PrintableNode rightChild           this title leftChild rightChild CLI PRINT COLOR BLACK              public PrintableNodeInfo String title  PrintableNode leftChild  PrintableNode righthild  CLI PRINT COLOR textColor           this title   title          this leftChild   leftChild          this rightChild   righthild          this textColor   textColor             public String getTitle            return title             public CLI PRINT COLOR getTextColor            return textColor             public String getTitleFormatted int max chars           return this textColor title CLI PRINT COLOR RESET                     String title   this title length    gt  max chars   this title substring 0 max chars 1  this title          boolean left   true          while title length    lt  max chars               if  left                   title       title                else                   title   title                                        return this textColor title CLI PRINT COLOR RESET               public int getTitleLength            return title length               public PrintableNodeInfo getLeftChildInfo            if  leftChild    null               return null                    return leftChild  getPrintableNodeInfo               public PrintableNodeInfo getRightChildInfo            if  rightChild    null               return null                    return rightChild  getPrintableNodeInfo              NodePosition class  package com tomac120 NodePrinter          Created by elijah on 6 28 16      public class PrintableNodePosition implements Comparable lt PrintableNodePosition gt        public final int row      public final int column      public final PrintableNodeInfo nodeInfo      public PrintableNodePosition PrintableNodeInfo nodeInfo  int row  int column           this row   row          this column   column          this nodeInfo   nodeInfo              Override     public int compareTo PrintableNodePosition o            return Integer compare this column o column             And  finally  Node Interface  package com tomac120 NodePrinter          Created by elijah on 6 28 16      public interface PrintableNode       PrintableNodeInfo  getPrintableNodeInfo        PrintableNode  getLeftChild        PrintableNode  getRightChild

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For those who looking for Rust solution   pub struct Node     pub value  i32    left  Option lt Box lt Node gt  gt     right  Option lt Box lt Node gt  gt     impl Node      pub fn new val  i32  - gt  Node       Node         value  val        left  None        right  None              pub fn getLeftNode  amp self  - gt  Option lt  amp Node gt       self left as deref          pub fn getRightNode  amp self  - gt  Option lt  amp Node gt       self right as deref          pub fn setLeftNode  amp mut self  val  i32  - gt   amp mut Node      self left   Some Box  new Node  new val        self left as deref mut   unwrap          pub fn setRightNode  amp mut self  val  i32  - gt   amp mut Node      self right   Some Box  new Node  new val        self right as deref mut   unwrap          fn visualizeTree  amp self  level  u16  is tail  bool  columns   amp mut HashSet lt u16 gt         let left   self getLeftNode        let right   self getRightNode         if right is some           right unwrap   visualizeTree level 1  false  columns              if level  gt  0         for i in 0  level-1             if columns contains  amp i                print                        else               print                                     if is tail           println    --      self value           columns remove  amp  level-1            columns insert level           else           println    --      self value           columns insert level           columns insert level-1                 else         println        self value              if left is some           left unwrap   visualizeTree level 1  true  columns                pub fn printTree  amp self        let mut columns   HashSet  new        columns insert 0       self visualizeTree 0  true   amp mut columns           The output is something like this    -- 17            -- 3                 -- 9       -- 2           -- 1 20       -- 7                 -- 16            -- 15  -- 8           -- 11      -- 4          -- 13

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public static class Node lt T extends Comparable lt T gt  gt        T value      Node lt T gt  left  right       public void insertToTree T v            if  value    null                value   v              return                    if  v compareTo value   lt  0                if  left    null                    left   new Node lt T gt                               left insertToTree v             else               if  right    null                    right   new Node lt T gt                               right insertToTree v                        public void printTree OutputStreamWriter out  throws IOException           if  right    null                right printTree out  true                         printNodeValue out           if  left    null                left printTree out  false                           private void printNodeValue OutputStreamWriter out  throws IOException           if  value    null                out write   lt null gt               else               out write value toString                       out write   n                 use string and not stringbuffer on purpose as we need to change the indent at each recursion     private void printTree OutputStreamWriter out  boolean isRight  String indent  throws IOException           if  right    null                right printTree out  true  indent    isRight                                                out write indent           if  isRight                out write                  else               out write                           out write  -----             printNodeValue out           if  left    null                left printTree out  false  indent    isRight                                                   will print                     ----- 20                           ----- 15           ----- 14                   ----- 13   ----- 12                   ----- 11           ----- 10                   ----- 9 8                   ----- 7           ----- 6                   ----- 5   ----- 4                   ----- 3           ----- 2                   ----- 1   for the input  8 4 12 2 6 10 14 1 3 5 7 9 11 13 20 15  this is a variant from  anurag s answer - it was bugging me to see the extra  s

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This is a very simple solution to print out a tree   It is not that pretty  but it is really simple   enum   kWidth   6    void PrintSpace int n      for  int i   0  i  lt  n    i      printf          void PrintTree struct Node   root  int level      if   root  return    PrintTree root- gt right  level   1     PrintSpace level   kWidth     printf   d   root- gt data     PrintTree root- gt left  level   1       Sample output          106             105 104             103                   102                         101       100

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I ve created simple binary tree printer  You can use and modify it as you want  but it s not optimized anyway  I think that a lot of things can be improved here     import java util ArrayList  import java util Collections  import java util List   public class BTreePrinterTest        private static Node lt Integer gt  test1             Node lt Integer gt  root   new Node lt Integer gt  2           Node lt Integer gt  n11   new Node lt Integer gt  7           Node lt Integer gt  n12   new Node lt Integer gt  5           Node lt Integer gt  n21   new Node lt Integer gt  2           Node lt Integer gt  n22   new Node lt Integer gt  6           Node lt Integer gt  n23   new Node lt Integer gt  3           Node lt Integer gt  n24   new Node lt Integer gt  6           Node lt Integer gt  n31   new Node lt Integer gt  5           Node lt Integer gt  n32   new Node lt Integer gt  8           Node lt Integer gt  n33   new Node lt Integer gt  4           Node lt Integer gt  n34   new Node lt Integer gt  5           Node lt Integer gt  n35   new Node lt Integer gt  8           Node lt Integer gt  n36   new Node lt Integer gt  4           Node lt Integer gt  n37   new Node lt Integer gt  5           Node lt Integer gt  n38   new Node lt Integer gt  8            root left   n11          root right   n12           n11 left   n21          n11 right   n22          n12 left   n23          n12 right   n24           n21 left   n31          n21 right   n32          n22 left   n33          n22 right   n34          n23 left   n35          n23 right   n36          n24 left   n37          n24 right   n38           return root             private static Node lt Integer gt  test2             Node lt Integer gt  root   new Node lt Integer gt  2           Node lt Integer gt  n11   new Node lt Integer gt  7           Node lt Integer gt  n12   new Node lt Integer gt  5           Node lt Integer gt  n21   new Node lt Integer gt  2           Node lt Integer gt  n22   new Node lt Integer gt  6           Node lt Integer gt  n23   new Node lt Integer gt  9           Node lt Integer gt  n31   new Node lt Integer gt  5           Node lt Integer gt  n32   new Node lt Integer gt  8           Node lt Integer gt  n33   new Node lt Integer gt  4            root left   n11          root right   n12           n11 left   n21          n11 right   n22           n12 right   n23          n22 left   n31          n22 right   n32           n23 left   n33           return root             public static void main String   args             BTreePrinter printNode test1             BTreePrinter printNode test2               class Node lt T extends Comparable lt   gt  gt        Node lt T gt  left  right      T data       public Node T data            this data   data           class BTreePrinter        public static  lt T extends Comparable lt   gt  gt  void printNode Node lt T gt  root            int maxLevel   BTreePrinter maxLevel root            printNodeInternal Collections singletonList root   1  maxLevel              private static  lt T extends Comparable lt   gt  gt  void printNodeInternal List lt Node lt T gt  gt  nodes  int level  int maxLevel            if  nodes isEmpty      BTreePrinter isAllElementsNull nodes               return           int floor   maxLevel - level          int endgeLines    int  Math pow 2   Math max floor - 1  0             int firstSpaces    int  Math pow 2   floor   - 1          int betweenSpaces    int  Math pow 2   floor   1   - 1           BTreePrinter printWhitespaces firstSpaces            List lt Node lt T gt  gt  newNodes   new ArrayList lt Node lt T gt  gt             for  Node lt T gt  node   nodes                if  node    null                    System out print node data                   newNodes add node left                   newNodes add node right                 else                   newNodes add null                   newNodes add null                   System out print                                  BTreePrinter printWhitespaces betweenSpaces                     System out println               for  int i   1  i  lt   endgeLines  i                  for  int j   0  j  lt  nodes size    j                      BTreePrinter printWhitespaces firstSpaces - i                   if  nodes get j     null                        BTreePrinter printWhitespaces endgeLines   endgeLines   i   1                       continue                                     if  nodes get j  left    null                      System out print                       else                     BTreePrinter printWhitespaces 1                    BTreePrinter printWhitespaces i   i - 1                    if  nodes get j  right    null                      System out print                        else                     BTreePrinter printWhitespaces 1                    BTreePrinter printWhitespaces endgeLines   endgeLines - i                              System out println                         printNodeInternal newNodes  level   1  maxLevel              private static void printWhitespaces int count            for  int i   0  i  lt  count  i                System out print                  private static  lt T extends Comparable lt   gt  gt  int maxLevel Node lt T gt  node            if  node    null              return 0           return Math max BTreePrinter maxLevel node left   BTreePrinter maxLevel node right     1             private static  lt T gt  boolean isAllElementsNull List lt T gt  list            for  Object object   list                if  object    null                  return false                     return true             Output 1             2                                                                                                 7       5                                                 2   6   3   6                         5 8 4 5 8 4 5 8    Output 2           2                                                                                       7       5                                           2   6       9                         5 8     4

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public void printPreety         List lt TreeNode gt  list   new ArrayList lt TreeNode gt         list add head       printTree list  getHeight head       public int getHeight TreeNode head         if  head    null            return 0        else           return 1   Math max getHeight head left   getHeight head right                    pass head node in list and height of the tree          param levelNodes     param level     private void printTree List lt TreeNode gt  levelNodes  int level         List lt TreeNode gt  nodes   new ArrayList lt TreeNode gt            indentation for first node in given level     printIndentForLevel level        for  TreeNode treeNode   levelNodes               print node data         System out print treeNode    null     treeNode data              spacing between nodes         printSpacingBetweenNodes level              if its not a leaf node         if level gt 1               nodes add treeNode    null  null treeNode left               nodes add treeNode    null  null treeNode right                       System out println         if level gt 1                   printTree nodes  level-1            private void printIndentForLevel int level       for  int i    int   Math pow 2 level-1    i  gt 0  i--            System out print                private void printSpacingBetweenNodes int level         spacing between nodes     for  int i    int    Math pow 2 level-1   2 -1  i  gt 0  i--            System out print                 Prints Tree in following format                  4                                        3               7                    1               5       8              2                       10                                 9

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Your tree will need twice the distance for each layer          a                                                  b       c                               d   e   f   g                 h i j k l m n o  You can save your tree in an array of arrays  one array for every depth     a   b c   d e f g   h i j k l m n o    If your tree is not full  you need to include empty values in that array          a                                                  b       c                               d   e   f   g                 h i   k l m   o   a   b c   d e f g   h i   k l m   o    Then you can iterate over the array to print your tree  printing spaces before the first element and between the elements depending on the depth and printing the lines depending on if the corresponding elements in the array for the next layer are filled or not  If your values can be more than one character long  you need to find the longest value while creating the array representation and multiply all widths and the number of lines accordingly

[java] How to print binary tree diagram?

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