Combination Sum

Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.

The same repeated number may be chosen from C unlimited number of times.

public class Solution {
        public ArrayList<ArrayList<Integer>> combinationSum(int[] candidates, int target) {
            ArrayList<Integer> output= new ArrayList<Integer>();
            ArrayList<ArrayList<Integer>> res = new ArrayList<ArrayList<Integer>>();
            if(candidates.length<=0) return res;
            Arrays.sort(candidates);//don't forget sort
            DFS(res,output,0,candidates,0,target);
            return res;
        }
        public void DFS(ArrayList<ArrayList<Integer>>res,ArrayList<Integer> output,int start,int[]can,int sum,int target){
            if(sum>target) return;
            if(sum==target){
                ArrayList<Integer> temp = new ArrayList<Integer>();
                temp.addAll(output);
                res.add(temp);
                return;
            }
            for(int i=start;i<can.length;i++){
                sum +=can[i];
                output.add(can[i]);
                DFS(res,output,i,can,sum,target);
                sum-=output.get(output.size()-1);
                output.remove(output.size()-1);
            }
        }
    }