Generate all subsets of size k

GenerateAllSubsetsOfSizeK.java

import java.util.ArrayList;
import java.util.List;

/*
   Problem: Generate all subsets of size k
   Ex. given n = 5 and k =2 generate [1, 2] [1, 3] [1, 4] [1, 5] [2, 3] [2, 4] [2, 5] [3, 4] [3, 5] [4, 5]

   Solution: This is backtracking problem in which you pass start index + 1 to next iteration of backtrack
*/
public class GenerateAllSubsetsOfSizeK {
   
    public List<List<Integer>> combination(int n, int k) {
        List<List<Integer>> result = new ArrayList<>();
        backtrack(n, k, 1, result, new ArrayList<>());
        return result;
    }

    public void backtrack(int n, int k, int startIndex, List<List<Integer>> result,
                          List<Integer> partialList) {
        if (k == partialList.size()) {
            result.add(new ArrayList<>(partialList));
            return;
        }
        for (int i = startIndex; i <= n; i++) {
            partialList.add(i);
            backtrack(n, k, i + 1, result, partialList);
            partialList.remove(partialList.size() - 1);
        }
    }

}