class Solution {
public:
    vector<vector<int>> result;
    vector<int> path;
    void backtraking(int k, int n , int sum ,int startidx)
    {
        if(path.size() == k && sum == n)
        {
            result.push_back(path);
            return;
        }else
        {
            for(int i= startidx ; i < 10 ; i++)
            {
                path.push_back(i);
                backtraking(k,n,sum+i,i+1);
                path.pop_back();
            }
            return;
        }
    }
    vector<vector<int>> combinationSum3(int k, int n) {
        backtraking(k,n,0,1);
        return result;
    }
};

class Solution {
public:
    vector<vector<int>> result;
    vector<int> path;
    void backtraking(int k, int n , int sum ,int startidx)
    {
        if(sum > n) return;
        if(path.size() == k && sum == n)
        {
            result.push_back(path);
            return;
        }else
        {
            for(int i= startidx ; i < 10 - (k - path.size()) + 1 ; i++)
            {
                path.push_back(i);
                backtraking(k,n,sum+i,i+1);
                path.pop_back();
            }
            return;
        }
    }
    vector<vector<int>> combinationSum3(int k, int n) {
        backtraking(k,n,0,1);
        return result;
    }
};

class Solution {
public:
    vector<vector<int>> result;
    vector<int> pathNum;
    void dfs(int k , int n , int sum ,int fir)
    {
        if(pathNum.size() == k && sum == n)
        {
            result.push_back(pathNum);
            return;
        }
        for(int i = fir ; i<=9 ; i++)
        {
            pathNum.push_back(i);
            dfs(k,n,sum+i,i+1);
            pathNum.pop_back();
        }
    }
    vector<vector<int>> combinationSum3(int k, int n) {
        dfs(k,n,0,1);
        return result;
    }
};