C linked list inserting node at the end

Question

I m having some trouble with my insertion method for a linked list in C  It seems to only add at the beginning of the list  Any other insertion I make fail  And this CodeBlocks debugger is so hard to understand I still don t get it  It never gives me value  just addresses in memory  Anyway this is my function  Do you see any reason why it s failing       function to add a new node at the end of the list    int addNodeBottom int val  node  head          create new node     node  newNode    node  malloc sizeof node         if newNode    NULL           fprintf stderr   Unable to allocate memory for new node n            exit -1              newNode- gt value   val         check for first insertion     if head- gt next    NULL           head- gt next   newNode          printf  added at beginning n               else                 else loop through the list and find the last           node  insert next to it         node  current   head          while current- gt next    NULL                        if current- gt next    NULL                                current- gt next   newNode                  printf  added later n                              current   current- gt next                      return 0      Then in main  only 929 is added        testing addNodeBottom function     addNodeBottom 929  head       addNodeBottom 98  head       addNodeBottom 122  head       addNodeBottom 11  head       addNodeBottom 1034  head

User · Answer

After you malloc a node make sure to set node- gt next   NULL   int addNodeBottom int val  node  head            node  current   head      node  newNode    node    malloc sizeof node        if  newNode    NULL            printf  malloc failed n            exit -1                  newNode- gt value   val      newNode- gt next   NULL       while  current- gt next            current   current- gt next                current- gt next   newNode      return 0          I should point out that with this version the head is still used as a dummy  not used for storing a value   This lets you represent an empty list by having just a head node

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The new node is always added after the last node of the given Linked List  For example if the given Linked List is 5- 10- 15- 20- 25 and we add an item 30 at the end  then the Linked List becomes 5- 10- 15- 20- 25- 30  Since a Linked List is typically represented by the head of it  we have to traverse the list till end and then change the next of last node to new node      Given a reference  pointer to pointer  to the head    of a list and an int  appends a new node at the end           void append struct node   head ref  int new data               1  allocate node             struct node  new node    struct node   malloc sizeof struct node             struct node  last    head ref      used in step 5           2  put in the data             new node- gt data    new data          3  This new node is going to be the last node  so make next            of it as NULL           new node- gt next   NULL          4  If the  lt a href     gt Linked List lt  a gt  is empty  then make the new node as head            if   head ref    NULL                    head ref   new node         return                      5  Else traverse till the last node            while  last- gt next    NULL          last   last- gt next          6  Change the next of last node            last- gt next   new node          return

User · Answer

I know this is an old post but just for reference   Here is how to append without the special case check for an empty list  although at the expense of more complex looking code   void Append List   l  Node   n        Node    next    amp list- gt Head      while   next    NULL  next    amp   next - gt Next       next   n      n- gt Next   NULL

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I would like to mention the key before writing the code for your consideration      Key  temp  address of new node allocated by malloc function  member od alloc h library in C    prev  address of last node of existing link list   next   contains address of next node   struct node       int data      struct node  next     head   void addnode end int a        struct node  temp   prev      temp    struct node   malloc sizeof node        if  temp    NULL            cout  lt  lt   Not enough memory         else           node- gt data   a          node- gt next   NULL          prev   head           while  prev- gt next    NULL                prev   prev- gt next                     prev- gt next   temp

User · Answer

This works fine   struct node  addNode node  head  int value        node  newNode    node    malloc sizeof node        newNode- gt value   value      newNode- gt next   NULL       if  head    NULL               Add at the beginning         head   newNode        else           node  current   head           while  current- gt next    NULL                current   current- gt next                         Add at the end         current- gt next   newNode             return head      Example usage   struct node  head   NULL   for  int currentIndex   1  currentIndex  lt  10  currentIndex          head   addNode head  currentIndex

User · Answer

This code will work  The answer from samplebias is almost correct  but you need a third change   int addNodeBottom int val  node  head          create new node     node  newNode    node  malloc sizeof node         if newNode    NULL           fprintf stderr   Unable to allocate memory for new node n            exit -1              newNode- gt value   val      newNode- gt next   NULL      Change 1        check for first insertion     if head- gt next    NULL           head- gt next   newNode          printf  added at beginning n               else                 else loop through the list and find the last           node  insert next to it         node  current   head          while  true       Change 2             if current- gt next    NULL                                current- gt next   newNode                  printf  added later n                    break     Change 3                           current   current- gt next                       return 0      Change 1  newNode- gt next must be set to NULL so we don t insert invalid pointers at the end of the list   Change 2 3  The loop is changed to an endless loop that will be jumped out with break  when we found the last element  Note how while current- gt next    NULL  contradicted if current- gt next    NULL  before   EDIT  Regarding the while loop  this way it is much better     node  current   head    while  current- gt next    NULL        current   current- gt next        current- gt next   newNode    printf  added later n

[c] C linked list inserting node at the end

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