C# Creating an array of arrays

Question

I'm trying to create an array of arrays that will be using repeated data, something like below:

int[] list1 = new int[4] { 1, 2, 3, 4 };
int[] list2 = new int[4] { 5, 6, 7, 8 };
int[] list3 = new int[4] { 1, 3, 2, 1 };
int[] list4 = new int[4] { 5, 4, 3, 2 };

int[,] lists = new int[4, 4] {  list1 ,  list2 ,  list3 ,  list4  };

I can't get it to work and so I'm wondering if I'm approaching this wrong.

What I'm attempting to do is create some sort of method to create a long list of the values so I can process them in a specific order, repeatedly. Something like,

int[,] lists = new int[90,4] { list1, list1, list3, list1, list2, (and so on)};

for (int i = 0; i < 90; ++i) {
   doStuff(lists[i]);
}

and have the arrays passed to doStuff() in order. Am I going about this entirely wrong, or am I missing something for creating the array of arrays?

score 79 · Accepted Answer · answered Feb 14 '09 at 17:37

79

What you need to do is this:

int[] list1 = new int[4] { 1, 2, 3, 4};
int[] list2 = new int[4] { 5, 6, 7, 8};
int[] list3 = new int[4] { 1, 3, 2, 1 };
int[] list4 = new int[4] { 5, 4, 3, 2 };

int[][] lists = new int[][] {  list1 ,  list2 ,  list3 ,  list4  };

Another alternative would be to create a List<int[]> type:

List<int[]> data=new List<int[]>(){list1,list2,list3,list4};

answered Feb 14 '09 at 17:37

Sean

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How do I create an empty array of arrays with a fixed size? The individual arrays stored within the array may vary, but there will be a fixed amount of arrays within the master array. – Aaron Franke Nov 03 '17 at 21:19
1

@AaronFranke I think you are asking for `int[][] lists = new int[n][];` where `n` is the number of arrays in your array of arrays. – Jeanot Zubler Nov 23 '22 at 12:56

score 10 · Answer 2 · answered Feb 14 '09 at 17:37

The problem is that you are attempting to define the elements in lists to multiple lists (not multiple ints as is defined). You should be defining lists like this.

int[,] list = new int[4,4] {
 {1,2,3,4},
 {5,6,7,8},
 {1,3,2,1},
 {5,4,3,2}};

You could also do

int[] list1 = new int[4] { 1, 2, 3, 4};
int[] list2 = new int[4] { 5, 6, 7, 8};
int[] list3 = new int[4] { 1, 3, 2, 1 };
int[] list4 = new int[4] { 5, 4, 3, 2 };

int[,] lists = new int[4,4] {
 {list1[0],list1[1],list1[2],list1[3]},
 {list2[0],list2[1],list2[2],list2[3]},
 etc...};

Noldorin · Answer 3 · 2017-11-16T00:31:21.017

8

I think you may be looking for Jagged Arrays, which are different from multi-dimensional arrays (as you are using in your example) in C#. Converting the arrays in your declarations to jagged arrays should make it work. However, you'll still need to use two loops to iterate over all the items in the 2D jagged array.

edited Nov 16 '17 at 00:31

answered Feb 14 '09 at 17:39

Noldorin

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The link in your answer simply redirects to a page about "The new Surface Pro". – Aaron Franke Nov 03 '17 at 21:21
This post is 8 years old... I think linkrot is to be expected! – Noldorin Nov 03 '17 at 21:45
2

Here's an up-to-date [MSDN document about jagged arrays](https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/arrays/jagged-arrays) – Anton Schwaighofer Nov 15 '17 at 21:52

score 0 · Answer 4 · answered Aug 14 '20 at 14:49

0

This loops vertically but might work for you.

int rtn = 0;    
foreach(int[] L in lists){
    for(int i = 0; i<L.Length;i++){
          rtn = L[i];
      //Do something with rtn
    }
}

answered Aug 14 '20 at 14:49

Robert Quinn

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score 0 · Answer 5 · answered Oct 06 '22 at 20:38

0

The following will give you an array in the iterator variable of foreach

int[][] ar =
{
    new []{ 50, 50, 1 },
    new []{ 80, 40, 2 },
    new []{ 10, 60, 3 },
    new []{ 51, 38, 4 },
    new []{ 48, 38, 5 }
};

answered Oct 06 '22 at 20:38

Richard Collette

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C# Creating an array of arrays

5 Answers5

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