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 }