Get all sub arrays of a particular length in an array

Question

I want help with getting the subsets of an array in C#. All other examples could not help me much.

I want to get all the subsets of a particular size of an array.

for example if input array is {1,2,3,4} and i want all subsets of size 3, all the unique subsets {1,2,3},{1,2,4},{2,3,4},{1,3,4} must be returned.

I am new to C# and any kind of help is much appreciated.

http://stackoverflow.com/questions/13765699/how-can-i-obtain-all-the-possible-combination-of-a-subset — I4V, Apr 16 '13 at 17:47
http://stackoverflow.com/questions/1952153/what-is-the-best-way-to-find-all-combinations-of-items-in-an-array — arunlalam, Apr 16 '13 at 18:19

score 0 · Answer 1 · edited May 23 '17 at 10:25

0

Check this article. This is described in detail with examples in all sorts of programming languages. I don't feel the need to copy others solutions so I will leave this as a link for you to choose from the MANY examples which should help you

Algorithm to return all combinations of k elements from n

edited May 23 '17 at 10:25

Community

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1

answered Apr 16 '13 at 18:00

Dave

478
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user1689571 · Answer 2 · 2013-04-16T18:43:49.340

Sounds suspiciously like a homework assignment....

Since I presume the size is variable, you'll want to use recursion. Something like:

    static void Main(string[] args)
    {
        int[] originalList = new int[] { 1, 2, 3, 4 };
        Stack<int> currentList = new Stack<int>();
        List<int[]> listOfSubsets = new List<int[]>();

        BuildListOfSubsets(originalList, listOfSubsets, 3, 0, currentList);
    }

    private static void BuildListOfSubsets(int[] originalList, List<int[]> listOfSubsets, int sizeOfSubsetList, int currentLevel, Stack<int> currentList)
    {
        if (currentList.Count == sizeOfSubsetList)
        {
            int[] copy = new int[sizeOfSubsetList];
            currentList.CopyTo(copy, 0);
            listOfSubsets.Add(copy);
        }
        else
            for (int ix = currentLevel; ix < originalList.Length; ix++)
            {
                currentList.Push(originalList[ix]);
                BuildListOfSubsets(originalList, listOfSubsets, sizeOfSubsetList, ix + 1, currentList);
                currentList.Pop();
            }
    }

The result will be in the listOfSubsets list. See if you can find an optimization to leave the for loop early.

Get all sub arrays of a particular length in an array

2 Answers2