[leetcode]216. Combination Sum III

[leetcode]216. Combination Sum III

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Analysis

电脑坏了—— [心塞！！]

Find all possible combinations of k numbers that add up to a number n, given that only numbers from 1 to 9 can be used and each combination should be a unique set of numbers.
Note:
All numbers will be positive integers.
The solution set must not contain duplicate combinations.
递归解决~

Implement

class Solution {
public:
    vector<vector<int>> combinationSum3(int k, int n) {
        vector<int> tmp;
        helper(k, n, 1, tmp);
        return res;
    }
    void helper(int k, int n, int l, vector<int>& tmp){
        if(n < 0)
            return ;
        if(n == 0 && tmp.size() == k)
            res.push_back(tmp);
        for(int i=l; i<=9; i++){
            tmp.push_back(i);
            helper(k, n-i, i+1, tmp);
            tmp.pop_back();
        }
    }
private:
    vector<vector<int>> res;
};