Combination Sum III Solutions in C++

// Source : https://leetcode.com/problems/combination-sum-iii/
// Author : Hao Chen
// Date   : 2015-06-11


#include <stdlib.h>
#include <iostream>
#include <vector>
using namespace std;

void combinationSumHelper(vector<int>& candidates, int start, int num, int target, 
                          vector<int>& solution, vector< vector<int> >& results) {
    if (target < 0|| solution.size() > num){
        return;
    }
    if (target == 0 && solution.size()==num){
        results.push_back(solution);
        return;
    }
    for (int i=start; i<candidates.size(); i++){
        solution.push_back(candidates[i]);
        combinationSumHelper(candidates, i+1, num, target-candidates[i], solution, results);
        solution.pop_back();
    }
    
}

vector< vector<int> > combinationSum3(int k, int n) {
    vector<int> v;
    for (int i=1; i<=9; i++){
        v.push_back(i);
    }

    vector< vector<int> > result;
    vector<int> solution;

    combinationSumHelper(v, 0, k, n, solution, result);    

    return result;

}

void PrintResults(int k, int n, vector< vector<int> >& results) {
    cout << "k=" << k << ", n=" << n << "\t";
    for (int i=0; i<results.size(); i++){
        cout << "[";
        for (int j=0; j<results[i].size(); j++){
            cout << results[i][j] << (j!=results[i].size()-1 ? ",":"]") ;
        }
        cout << ( i!=results.size()-1 ? ", " : "" );
    } 
    cout << endl;
}

int main(int argc, char** argv) 
{
    int k = 3, n =9;
    if (argc > 2){
        k = atoi(argv[1]);
        n = atoi(argv[2]);
    } 

    vector< vector<int> > results;
    results = combinationSum3(k, n);

    PrintResults(k,n, results);
    return 0;
}

/// Source : https://leetcode.com/problems/combination-sum-iii/description/
/// Author : liuyubobobo
/// Time   : 2018-03-04

#include <iostream>
#include <vector>

using namespace std;


class Solution {
public:
    vector<vector<int>> combinationSum3(int k, int n) {

        vector<vector<int>> res;
        vector<int> cur_res;
        solve(1, k, n, cur_res, res);
        return res;
    }

private:
    void solve(int index, int k, int n,
               vector<int>& cur_res, vector<vector<int>>& res){

        if(n == 0 && k == 0){
            res.push_back(cur_res);
            return;
        }

        if(k == 0)
            return;

        for(int i = index ; i <= 9 ; i ++)
            if(n >= i){
                cur_res.push_back(i);
                solve(i + 1, k - 1, n - i, cur_res, res);
                cur_res.pop_back();
            }

        return;
    }
};

void print_vec(const vector<int>& vec){
    for(int e: vec)
        cout << e << " ";
    cout << endl;
}

int main() {

    vector<vector<int>> res1 = Solution().combinationSum3(3, 7);
    for(const vector<int>& a_res: res1)
        print_vec(a_res);

    cout << endl;

    vector<vector<int>> res2 = Solution().combinationSum3(3, 9);
    for(const vector<int>& a_res: res2)
        print_vec(a_res);

    return 0;
}