Leetcode: Combination Sum II

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

Each number in C may only be used once in the combination.

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 10,1,2,7,6,1,5 and target 8, 
A solution set is: 
[1, 7] 
[1, 2, 5] 
[2, 6] 
[1, 1, 6] 

 1 public class Solution {
 2     public ArrayList<ArrayList<Integer>> combinationSum2(int[] num, int target) {
 3         ArrayList<ArrayList<Integer>> res = new ArrayList<ArrayList<Integer>>();
 4         if (num == null || num.length == 0) return res;
 5         ArrayList<Integer> path = new ArrayList<Integer>();
 6         Arrays.sort(num);
 7         helper(res, path, num, target, 0, 0);
 8         return res;
 9     }
10     
11     public void helper(ArrayList<ArrayList<Integer>> res, ArrayList<Integer> path, int[] num, int target, int accum, int index) {
12         if (accum > target) return;
13         if (accum == target) {
14             if (!res.contains(path)) res.add(new ArrayList<Integer>(path));
15             return;
16         }
17         for (int i=index; i<num.length; i++) {
18             path.add(num[i]);
19             helper(res, path, num, target, accum+num[i], i+1);
20             path.remove(path.size()-1);
21         }
22     }
23 }

 1 public ArrayList<ArrayList<Integer>> combinationSum2(int[] num, int target) {
 2     ArrayList<ArrayList<Integer>> res = new ArrayList<ArrayList<Integer>>();
 3     if(num == null || num.length==0)
 4         return res;
 5     Arrays.sort(num);
 6     helper(num,0,target,new ArrayList<Integer>(),res);
 7     return res;
 8 }
 9 private void helper(int[] num, int start, int target, ArrayList<Integer> item,
10 ArrayList<ArrayList<Integer>> res)
11 {
12     if(target == 0)
13     {
14         res.add(new ArrayList<Integer>(item));
15         return;
16     }
17     if(target<0 || start>=num.length)
18         return;
19     for(int i=start;i<num.length;i++)
20     {
21         if(i>start && num[i]==num[i-1]) continue;
22         item.add(num[i]);
23         helper(num,i+1,target-num[i],item,res);
24         item.remove(item.size()-1);
25     }
26 }