import java.util.ArrayList;

import java.util.List;

class Solution {

public List<List<Integer>> combinationSum(int[] candidates, int target) {

List<List<Integer>> answer = new ArrayList<>();

makeCombination(candidates, target, 0, new ArrayList<>(), 0, answer);

return answer;

}

private void makeCombination(int[] candidates,

int target,

int idx,

List<Integer> comb,

int total,

List<List<Integer>> res) {

if (total == target) {

res.add(new ArrayList<>(comb));

return;

}

if (total > target || idx >= candidates.length) {

return;

}

comb.add(candidates[idx]);

makeCombination(candidates, target, idx, comb, total + candidates[idx], res);

comb.remove(comb.size() - 1);

makeCombination(candidates, target, idx + 1, comb, total, res);

}

}