Find all subsets of length k in an array

Question

Given a set {1,2,3,4,5...n} of n elements, we need to find all subsets of length k .

For example, if n = 4 and k = 2, the output would be

Answer 1

Here is a Java version of what I think Simple is talking about, using a binary representation of all sets in the power set. It's similar to how Abhiroop Sarkar did it, but I think a boolean array makes more sense than a string when you are just representing binary values.

private ArrayList> getSubsets(int m, Object[] objects){
    // m = size of subset, objects = superset of objects
    ArrayList> subsets = new ArrayList<>();
    ArrayList pot = new ArrayList<>();
    int n = objects.length;
    int p = 1;
    if(m==0)
        return subsets;
    for(int i=0; i<=n; i++){
        pot.add(p);
        p*=2;
    }
    for(int i=1; i=0; j--){
            int currentPot = pot.get(j);
            if(y >= currentPot){
                binArray[j] = true;
                y -= currentPot;
                sum++;
            }
            if(y<=0)
                break;
        }
        if(sum==m){
            ArrayList