How to find a one dimensional array in a two dimensional array in C#

Question

I have a two dimensional array namely States. I create a one dimensional array, say SubState. Then I change SubState. I want to find new SubState in States and get the index. As an example:

int[][] States = new int[3][] { new int[] { 3, 3, 4 }, new int[] { 2, 5, 1 }, new int[] { 2, 3, 4 } };
int[] SubState = new int[States[0].Length];
States[0].CopyTo(SubState, 0);
SubState[0] -= 1;

I want to find the index of new SubState in State, which will be 2 in the example. Thanks.

What is the problem that you're trying to solve? Your question doesn't make much sense and this approach doesn't seem very flexible or maintainable. — xxbbcc, Aug 07 '15 at 16:55
FYI that's not a 2 dimensional array, that's a jagged array. A 2 dimensional array would be defined as `int[3,3]`. — juharr, Aug 07 '15 at 17:00
I have a two dimensional array which contains some one dimensional arrays. Some of these arrays differ each other in one element. For example [3,3,4] differs with [2,3,4] & [3,2,4] &[3,3,3] in one element by 1. I want to find indices of these three arrays in the the main two dimensional array. — M. Mohebbi, Aug 07 '15 at 17:05
Thank you very much. As a beginner, I have made a lot of mistakes :). — M. Mohebbi, Aug 07 '15 at 17:13

score 1 · Answer 1 · edited May 23 '17 at 12:30

1

You're looking for SequenceEqual:

int index = -1;
for (int i = 0; i < States.Length; i++)
    if (States[i].SequenceEqual(SubState))
    {
        index = i;
        break;
    }

If you define a LINQ FindIndex operator, you can express it more concisely using:

int index = States.FindIndex(s => s.SequenceEqual(SubState));

edited May 23 '17 at 12:30

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answered Aug 07 '15 at 16:57

Douglas

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Thank you very much. That really helped. It would be appreciated if you tell me how to define a LINQ FindIndex operator too. Thanks. – M. Mohebbi Aug 07 '15 at 17:15
@M.Mohebbi: You can copy the implementation from the linked answer: http://stackoverflow.com/a/2471631/1149773 – Douglas Aug 07 '15 at 18:01

score 0 · Answer 2 · answered Aug 07 '15 at 16:58

You can use SequenceEqual method inside a LINQ query, like this:

var nextStateIndex = States
    .Select((a, i) => new {Index = i, Array = a})
    .FirstOrDefault(p => p.Array.SequenceEqual(SubState))
    ?.Index;
if (nextStateIndex.HasValue) {
    ...
}

Note: this code uses the new ?. operator. If you are targeting C# version that does not have support for this operator, store FirstOrDefault result for an explicit null checking.

score 0 · Answer 3 · answered Aug 07 '15 at 17:19

0

You can use Linq:

  var index = -1;

  var foundSubState = States.FirstOrDefault(x => {
    index++;
    return x.SequenceEqual(SubState);
  });

  var res = foundSubState != default(Array) ? index : -1;

answered Aug 07 '15 at 17:19

HashPsi

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How to find a one dimensional array in a two dimensional array in C#

3 Answers3