[Leetcode]_40 Combination Sum II

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/** *  Index: 40 *  Title: Combination Sum II *  Author: ltree98 **/

和39一样，也是用回溯解决。
但是，备用数组内的数字只能使用一次。

class Solution {private:    void traversalAll(vector<int>& candidates, int target, int index, vector<vector<int>>& ans, vector<int> perAns, int perAnsSum)  {        for(int i = index; i < candidates.size(); i++)  {            if(i != index && candidates[i] == candidates[i-1])                continue;            if(perAnsSum + candidates[i] == target) {                perAns.push_back(candidates[i]);                ans.push_back(perAns);                return;            }            else if(perAnsSum + candidates[i] < target)   {                perAns.push_back(candidates[i]);                perAnsSum += candidates[i];                traversalAll(candidates, target, i+1, ans, perAns, perAnsSum);                perAnsSum -= candidates[i];                perAns.pop_back();            }            else    {                return;            }        }    }public:    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {        std::sort(candidates.begin(), candidates.end());        vector<vector<int>> ans = vector<vector<int>>();        vector<int> perAns = vector<int>();        traversalAll(candidates, target, 0, ans, perAns, 0);        return ans;    }};

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