[LeetCode] 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> &num, int target) {
        sort(num.begin(), num.end());
        vector<vector<int>> res;
        vector<int> path;
        dfs(res, path, num, target, 0);
        return res;
    }
    void dfs(vector<vector<int>> &res, vector<int> &path, vector<int> &num, int target, int idx)
    {
        if(target < 0)  return;
        if(target == 0)
        {
            res.push_back(path);
            return;
        }
        for(int i = idx; i < num.size(); i++)
        {
            path.push_back(num[i]);
            dfs(res, path, num, target - num[i], i+1);
            path.pop_back();
            while(i < num.size() - 1 && num[i] == num[i+1]) i++;
        }
    }
};