Leetcode: 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.

Note:
All numbers (including target) will be positive integers.
Elements in a combination (a1, a2, … , ak) must be in non-descending order. (ie, a1 ≤ a2 ≤ … ≤ ak).
The solution set must not contain duplicate combinations.
For example, given candidate set 2,3,6,7 and target 7, 
A solution set is: 
[7] 
[2, 2, 3] 

 1 public class Solution {
 2     public ArrayList<ArrayList<Integer>> combinationSum(int[] candidates, int target) {
 3         ArrayList<ArrayList<Integer>> res = new ArrayList<ArrayList<Integer>>();
 4         ArrayList<Integer> path = new ArrayList<Integer>();
 5         java.util.Arrays.sort(candidates);
 6         findpaths(res, path, candidates, target);
 7         return res;
 8     }
 9     
10     public void findpaths(ArrayList<ArrayList<Integer>> res, ArrayList<Integer> path, int[] candidates, int remain) {
11         if (remain == 0) {
12             res.add(new ArrayList<Integer>(path));
13             return;
14         }
15         if (remain < 0) {
16             return;
17         }
18         for (int c : candidates) {
19             if (path.size() != 0 && c < path.get(path.size() - 1)) continue;
20             path.add(c);
21             remain = remain - c;
22             findpaths(res, path, candidates, remain);
23             remain = remain + c;
24             path.remove(path.size() - 1);
25         }
26     }
27 }