[LeetCode] #40 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]

本题与上题类似，不过首先需要对数组进行排序，然后需要去除重复。时间：8ms。代码如下：

class Solution {
public:
    void makeCombination2(vector<vector<int>>& ret, vector<int>& candidates, vector<int>& v, int target, int cur){
        if (target == 0){
            ret.push_back(v);
            return;
        }
        int rep = -1;
        for (size_t i = cur; i < candidates.size(); ++i){
            if (rep == candidates[i])
                continue;
            if (target >= candidates[i]){
                rep = candidates[i];
                v.push_back(candidates[i]);
                makeCombination2(ret, candidates, v, target - candidates[i], i + 1);
                v.pop_back();
            }
            else
                return;
        }
    }
    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {
        vector<vector<int>> ret;
        sort(candidates.begin(), candidates.end());
        if (candidates.empty() || target < candidates[0])
            return ret;
        vector<int> v;
        makeCombination2(ret, candidates, v, target, 0);
        return ret;
    }
};