day25 - 回溯算法part02

class Solution {
public:
    vector<vector<int>> result;
    vector<int> path;
    int sum = 0;

    void dfs(int k, int n, int start){
        if(path.size() == k){
            if(sum == n) result.push_back(path);
            return;
        }
        for(int i=start; i<=9; i++){
            path.push_back(i);
            sum += i;
            dfs(k, n, i+1);
            path.pop_back();
            sum -= i;
        }
    }

    vector<vector<int>> combinationSum3(int k, int n) {
        dfs(k, n, 1);
        return result;
    }
};