Combination Sum II

1. Title

Combination Sum II

2. Http address

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

3. The question

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]

4. My code(AC)

 1     //Accepted
 2        public List<List<Integer>> combinationSum2(int[] candidates, int target) {
 3 
 4             List<List<Integer>> result = new ArrayList<List<Integer>>();
 5             if( candidates == null)
 6                 return result;
 7             
 8             int len  = candidates.length;
 9             int sum = 0;
10             List<Integer> subList = new ArrayList<Integer>();
11             Arrays.sort(candidates);
12             for(int i = 0 ; i < len; i++)
13             {
14                 sum = candidates[i];
15                 subList.add(candidates[i]);
16                 getCombinationSum(candidates, i + 1, sum ,target,subList, result);
17                 sum = 0;
18                 subList.remove(0);
19             }
20             return result;   
21           }
22         private void getCombinationSum(int[] candidates, int begin, int sum,
23                 int target, List<Integer> subList, List<List<Integer>> result) {
24 
25             if( sum > target)
26             {
27                 return;
28             }
29             if( sum == target)
30             {
31                 List<Integer> add = new ArrayList<Integer>(subList);
32                 if( !result.contains(add))
33                     result.add(new ArrayList<Integer>(subList));
34                 return;
35             }
36             
37             int len = candidates.length;
38             for(int i = begin; i < len; i++)
39             {
40                     sum += candidates[i];
41                     subList.add(candidates[i]);
42                     getCombinationSum(candidates, i + 1, sum, target, subList, result);
43                     subList.remove(subList.size() -1);
44                     sum -= candidates[i];
45             }
46         }