Iterate Multi-Dimensional Array with Nested Foreach Statement

Question

I think this might be a pretty simple question  but I haven t been able to figure it out yet  If I ve got a 2-dimensional array like so   int    array   new int 2 3     1  2  3    4  5  6       What s the best way to iterate through each dimension of the array with a nested foreach statement

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Here s how to visit each element in a 2-dimensional array   Is this what you were looking for   for  int i 0 i lt array GetLength 0  i          for  int j 0 j lt array GetLength 1  j                  int cell   array i j

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If you want to iterate over every item in the array as if it were a flattened array  you can just do   foreach  int i in array        Console Write i       which would print     123456   If you want to be able to know the x and y indexes as well  you ll need to do   for  int x   0  x  lt  array GetLength 0   x    1        for  int y   0  y  lt  array GetLength 1   y    1            Console Write array x  y              Alternatively you could use a jagged array instead  an array of arrays    int     array   new int 2      new int 3   1  2  3   new int 3   4  5  6     foreach  int   subArray in array        foreach  int i in subArray            Console Write i             or  int     array   new int 2      new int 3   1  2  3   new int 3   4  5  6     for  int j   0  j  lt  array Length  j    1        for  int k   0  k  lt  array j  Length  k    1            Console Write array j  k

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I know this is an old post  but I found it through Google  and after playing with it think I have an easier solution   If I m wrong please point it out   cuz I d like to know  but this worked for my purposes at least  It s based off of ICR s response    for  int x   0  x  lt  array GetLength 0   x          Console Write array x  0   array x 1   array x 2        Since the both dimensions are limited  either one can be simple numbers  and thus avoid a nested for loop   I admit I m new to C   so please  if there s a reason not to do it  please tell me

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The 2D array in C  does not lend itself well to a nested foreach  it is not the equivalent of a jagged array  an array of arrays   You could do something like this to use a foreach  foreach  int i in Enumerable Range 0  array GetLength 0        foreach  int j in Enumerable Range 0  array GetLength 1            Console WriteLine array i  j      But you would still use i and j as index values for the array  Readability would be better preserved if you just went for the garden variety for loop instead

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Use LINQ  Cast lt int gt    to convert 2D array to IEnumerable lt int gt    LINQPad example   var arr   new int           1  2  3         4  5  6        IEnumerable lt int gt  values   arr Cast lt int gt     Console WriteLine values     Output

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You can use an extension method like this   internal static class ArrayExt       public static IEnumerable lt int gt  Indices this Array array  int dimension                for  var i   array GetLowerBound dimension   i  lt   array GetUpperBound dimension   i                          yield return i                      And then   int    array       1  2  3      4  5  6      foreach  var i in array Indices 0         foreach  var j in array Indices 1                 Console Write array i  j               Console WriteLine        It will be a bit slower than using for loops but probably not an issue in most cases  Not sure if it makes things more readable   Note that c  arrays can be other than zero-based so you can use a for loop like this   int    array       1  2  3      4  5  6      for  var i   array GetLowerBound 0   i  lt   array GetUpperBound 0   i          for  var j  array GetLowerBound 1   j  lt   array GetUpperBound 1   j                  Console Write array i  j               Console WriteLine

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I was looking for a solution to enumerate an array of an unknown at compile time rank with an access to every element indices set  I saw solutions with yield but here is another implementation with no yield  It is in old school minimalistic way  In this example AppendArrayDebug   just prints all the elements into StringBuilder buffer   public static void AppendArrayDebug   StringBuilder sb  Array array         if  array    null    array Length    0                 sb Append    lt nothing gt              return             int i       var rank   array Rank      var lastIndex   rank - 1          Initialize indices and their boundaries     var indices   new int rank       var lower   new int rank       var upper   new int rank       for  i   0  i  lt  rank    i                 indices i    lower i    array GetLowerBound  i            upper i    array GetUpperBound  i               while  true                 BeginMainLoop              Begin work with an element          var element   array GetValue  indices             sb AppendLine            sb Append                 for  i   0  i  lt  rank    i                         sb Append  indices i                 sb Append                           sb Length -  1          sb Append                    sb Append  element                End work with the element             Increment index set             All indices except the first one are enumerated several times         for  i   lastIndex  i  gt  0                          if    indices i   lt   upper i                    goto BeginMainLoop              indices i    lower i               --i                        Special case for the first index  it must be enumerated only once         if    indices 0   gt  upper 0                break            For example the following array will produce the following output   var array   new                 1   2   3       4   5   6       7   8   9      10  11  12              13  14  15      16  17  18      19  20  21      22  23  24            Output    0 0 0    1  0 0 1    2  0 0 2    3  0 1 0    4  0 1 1    5  0 1 2    6  0 2 0    7  0 2 1    8  0 2 2    9  0 3 0    10  0 3 1    11  0 3 2    12  1 0 0    13  1 0 1    14  1 0 2    15  1 1 0    16  1 1 1    17  1 1 2    18  1 2 0    19  1 2 1    20  1 2 2    21  1 3 0    22  1 3 1    23  1 3 2    24

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With multidimensional arrays  you can use the same method to iterate through the elements  for example   int    numbers2D   new int 3  2      9  99      3  33      5  55      foreach  int i in numbers2D        System Console Write   0     i           The output of this example is   9 99 3 33 5 55    References   MSDN  Using foreach with Arrays     In Java  multidimensional arrays are array of arrays  so the following works       int     table                   1  2  3                  4  5  6               for  int   row   table            for  int el   row                System out println el

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Two ways    Define the array as a jagged array  and use nested foreachs  Define the array normally  and use foreach on the entire thing    Example of  2    int    arr       1  2      3  4      foreach int a in arr      Console Write a      Output will be 1234  ie  exactly the same as doing i from 0 to n  and j from 0 to n

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As mentioned elsewhere  you can just iterate over the array and it will produce all results in order across all dimensions  However  if you want to know the indices as well  then how about using this - http   blogs msdn com b ericlippert archive 2010 06 28 computing-a-cartesian-product-with-linq aspx  then doing something like   var dimensionLengthRanges   Enumerable Range 0  myArray Rank  Select x   gt  Enumerable Range 0  myArray GetLength x     var indicesCombinations   dimensionLengthRanges CartesianProduct     foreach  var indices in indicesCombinations        Console WriteLine    0      1    string Join      indices   myArray GetValue indices ToArray

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You can also use enumerators  Every array-type of any dimension supports the Array GetEnumerator method  The only caveat is that you will have to deal with boxing unboxing  However  the code you need to write will be quite trivial   Here s the sample code   class Program       static void Main string   args                int    myArray   new int        1  2      3  4      5  6              var e   myArray GetEnumerator             e Reset             while  e MoveNext                             this will output each number from 1 to 6               Console WriteLine e Current ToString                        Console ReadLine

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int    arr                        1  2  3                    4  5  6                    7  8  9                    for int i   0  i  lt  arr GetLength 0   i           for  int j   0  j  lt  arr GetLength 1   j               Console Write    0  t  arr i  j          Console WriteLine           output   1  2  3          4  5  6          7  8  9

[c#] Iterate Multi-Dimensional Array with Nested Foreach Statement

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