iJade - 10 months ago 83

C# Question

how can we find out different combination of the elements of an array using c# code.

are there any inbuilt library function for this.?

for eg: suppose an array has elements {2,3,4,5,6,7}

then the possible combination would be 2,3,4,5,6,7,2 3,2 3 4,2 3 4 5, etc

so basically wat i need is a function which gives different combination based on its input for eg: comb(array,2) gives output 2 3,1 2,3 4 and comb(array,3) gives output 1 2 3,2 3 4,3 4 5 and so on

Eg: valid comnbination for array= {1, 2, 3} and length = 2 are 1 2,1 3,2 3 .....

Answer Source

```
static void Main()
{
var cnk = comb(new [] {1,2,3},2);
foreach ( var c in cnk)
{
}
}
public static IEnumerable<int[]> comb(int[] a, int k)
{
if (a == null || a.Length == 0 || k < 1 || k > a.Length)
yield break;
int n = a.Length;
// 1
if ( k == 1)
for ( int i = 0; i < n; i++)
{
yield return new int[] {a[i]};
}
else
{
// k
for ( int i = 0; i < n - k + 1; i++)
{
var res = new int[k];
for (int t = i, c = 0; t < i + k - 1; t++, c++)
res[c] = a[t];
for (int j = i + k - 1; j < n; j++)
{
res[k-1] = a[j];
yield return res;
}
}
}
}
```

You should take the algorithm from here, ~~my answer doesn't solve your problem~~
Algorithm to return all combinations of k elements from n