LeetCode 39. Combination Sum

题意

给定一个不重复的序列和一个 target ，序列中的每个数可以取多次，求取出数的和为 target 的方案

思路

直接DFS求出每个数要取几个即可

代码

class Solution {
public:
    vector<vector<int>> combinationSum(vector<int>& candidates, int target) {
        sort(candidates.begin(), candidates.end());
        vector<int>now;
        vector<vector<int> >ans;
        findAns(candidates, ans, now, 0, target);
        return ans;
    }
private:
    void findAns(vector<int>& candidates, vector<vector<int> >& ans, vector<int>& now, int id, int target){
        if(target == 0){
            ans.push_back(now);
            return ;
        }
        if(id >= candidates.size()) return ;
        for(int i = 0; i * candidates[id] <= target; i++){
            for(int j = 0; j < i; j++){
                now.push_back(candidates[id]);
            }
            findAns(candidates, ans, now, id + 1, target - i * candidates[id]);
            for(int j = 0; j < i; j++){
                now.pop_back();
            }
        }
    }
};