Combination Sum II

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] 

Code:

class Solution {
public:
    void findSum(vector<int> &S,int sum,int level,int &t,vector<int> &buf,vector<vector<int>> &res){
        for(int i=level;i<S.size();i++){
            buf.push_back(S[i]);
            if(sum+S[i]==t)
                res.push_back(buf);
            if(sum+S[i]<=t&&i<S.size()-1)
                findSum(S,sum+S[i],i+1,t,buf,res);
            buf.pop_back();
            while(i<S.size()-1&&S[i]==S[i+1])
                i++;
        }
    }
    vector<vector<int> > combinationSum2(vector<int> &num, int target) {
        vector<int> buf;
        vector<vector<int>> res;
        sort(num.begin(),num.end());
        findSum(num,0,0,target,buf,res);
        return res;
    }
};