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]

class Solution {
public:
    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {
        sort(candidates.begin(), candidates.end());
        vector<vector<int> > result;
        vector<int> temp;
        
        dfs(candidates, target, result, temp, 0);
        return result;
    }
    
    void dfs(vector<int>& candidates, int diff, vector<vector<int> >& result, vector<int>& temp, int start){
        if(diff == 0){
            result.push_back(temp);
            return;
        }
        
        for(int i = start; i < candidates.size(); i++){
            if(diff < candidates[i]) return;
            
            //only add the first number into the vector if there are many
            if(i > start && candidates[i] == candidates[i - 1]) continue;
            
            temp.push_back(candidates[i]);
            dfs(candidates, diff - candidates[i], result, temp, i + 1);
            temp.pop_back();
        }
        
    }
};