Combination Sum II [LeetCode]

Problem description: http://oj.leetcode.com/problems/combination-sum-ii/

Basic idea: use recursive approach, remember to avoid duplicate item.

 class Solution {
 public:
     bool isExist(vector<vector<int> > &combinations, vector<int> &item) {
         for(auto com: combinations){
             if(com.size() == item.size()){
                 int k;
                 for(k = ; k < com.size(); k++){
                     if(com[k] != item[k])
                         break;
                 }
                 if(k == com.size())
                     return true;
             }
         }
         return false;
     }
     vector<vector<int> > combinationSum2(vector<int> &num, int target) {
         // Note: The Solution object is instantiated only once and is reused by each test case.
         vector<vector<int> >  combinations;
         std::sort(num.begin(), num.end());
         int is_target_equal_to_num = ;
         for(int i = ; i < num.size(); i ++){
             if(num[i] == target && !is_target_equal_to_num){
                 is_target_equal_to_num = ;
                 vector<int> combination(, target);
                 combinations.push_back(combination);
             }else if(num[i] > target) {
                 break;
             }else {
                 vector<int> sub_num(num.begin() + i + , num.end());
                 vector<vector<int> > sub_combinations = combinationSum2(sub_num, target - num[i]);
                 for (auto item : sub_combinations) {
                     item.insert(item.begin(), num[i]);
                     if(!isExist(combinations, item))
                         combinations.push_back(item);
                 }
             }
         }

         return combinations;
     }
 };