https://leetcode.com/problems/combination-sum

gistfile1.txt

class Solution {
    
    public List<List<Integer>> combinationSum(int[] candidates, int target) {
        return new ArrayList<>(findComb(candidates, target));
    }
    
    Set<List<Integer>> findComb(int[] candidates, int target){
        Set<List<Integer>> result = new HashSet<List<Integer>>();
        for(int i = 0; i < candidates.length; i++){
            if(candidates[i] == target){
                List<Integer> comb = new ArrayList<Integer>();
                comb.add(target);
                result.add(comb);
            }
            if(candidates[i] < target){
                Set<List<Integer>> combs = findComb(candidates, target - candidates[i]);
                for(List<Integer> comb : combs){
                    comb.add(candidates[i]);
                    Collections.sort(comb);
                }
                result.addAll(combs);
            }
        }
        return result;
    }
}