Given an array, how to generate all combinations of subset size k?

Question

So given input = [1, 2, 3] and k=2 this would return:

1 2
1 3
2 1
2 3
3 1
3 2

This is the closest to what I am lo

Answer 1

Instead of combinations, try permutations.

Try generating permutations, then resizing the array.

Here's it implemented, modified from here

var permArr = [],
  usedChars = [];

function permute(input, k) {
  var i, ch;
  for (i = 0; i < input.length; i++) {
    ch = input.splice(i, 1)[0];
    usedChars.push(ch);
    if (input.length == 0) {
      var toadd = usedChars.slice(0,k);
      if(!permArr.includes(toadd)) permArr.push(toadd); // resizing the returned array to size k
    }
    permute(input, k);
    input.splice(i, 0, ch);
    usedChars.pop();
  }
  return permArr
};
console.log(JSON.stringify(permute([1, 2, 3], 2)));