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, � , a_k) must be in non-descending order. (ie, a₁ ? a₂ ? � ? a_k).
• 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] 

---

check dup

check target ==0 first!!!

public class Solution {    public ArrayList
     
      
       > combinationSum2(int[] num, int target) {        Arrays.sort(num);                ArrayList
       
        
         > rst = new ArrayList
         
          
           >(); ArrayList
           
             list = new ArrayList
            
             (); helper(num, 0, target, list, rst); return rst; } private void helper(int[] arr, int index, int target, ArrayList
             
               list, ArrayList
              
               
                > rst) { if (target == 0) { // Done ArrayList
                
                  l = new ArrayList
                 
                  (list); rst.add(l); return; } if (index < 0 || index >= arr.length || target < 0) return; for (int i = index; i < arr.length; ++i) { if (arr[i] > target) break; // check dup if(i>index && arr[i]==arr[i-1]) continue; list.add(arr[i]); helper(arr, i+1, target - arr[i], list, rst); list.remove(list.size() - 1); } }}