[LeetCode] Combination Sum III

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.

Ensure that numbers within the set are sorted in ascending order.

Example 1:

Input: k = 3, n = 7

Output:

[[1,2,4]]

Example 2:

Input: k = 3, n = 9

Output:

[[1,2,6], [1,3,5], [2,3,4]]

class Solution {
    void solve(vector<vector<int>> &res, vector<int> &one, int k, int s, int e)
    {
        if(e == 0 && k == 0)
        {   
            res.push_back(one);
            return;
        }

        for(int i=s;i<=e && i<=9;i++)
        {
            one.push_back(i);
            solve(res, one, k-1,i+1, e-i);
            one.pop_back();
        }
    }
public:

    vector<vector<int>> combinationSum3(int k, int n) {
        vector<vector<int>> res;
        vector<int> one;
        solve(res, one, k, 1, n);
        return res;
    }
};