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)

    //Accepted
       public List<List<Integer>> combinationSum2(int[] candidates, int target) {

            List<List<Integer>> result = new ArrayList<List<Integer>>();
            if( candidates == null)
                return result;
            
            int len  = candidates.length;
            int sum = 0;
            List<Integer> subList = new ArrayList<Integer>();
            Arrays.sort(candidates);
            for(int i = 0 ; i < len; i++)
            {
                sum = candidates[i];
                subList.add(candidates[i]);
                getCombinationSum(candidates, i + 1, sum ,target,subList, result);
                sum = 0;
                subList.remove(0);
            }
            return result;   
          }
        private void getCombinationSum(int[] candidates, int begin, int sum,
                int target, List<Integer> subList, List<List<Integer>> result) {

            if( sum > target)
            {
                return;
            }
            if( sum == target)
            {
                List<Integer> add = new ArrayList<Integer>(subList);
                if( !result.contains(add))
                    result.add(new ArrayList<Integer>(subList));
                return;
            }
            
            int len = candidates.length;
            for(int i = begin; i < len; i++)
            {
                    sum += candidates[i];
                    subList.add(candidates[i]);
                    getCombinationSum(candidates, i + 1, sum, target, subList, result);
                    subList.remove(subList.size() -1);
                    sum -= candidates[i];
            }
        }