LeetCode Combinations

Description

Given two integers n and k, return all possible combinations of k numbers out of 1 … n.

For example,
If n = 4 and k = 2, a solution is:

[
  [2,4],
  [3,4],
  [2,3],
  [1,2],
  [1,3],
  [1,4],
]

The original problem is here.

The original code is here.

My Solution

I solve this problem in C++, as below:

/*
*Combinations   
*Author: shuaijiang
*Email: zhaoshuaijiang8@gmail.com
*/
#include<iostream>
#include<vector>
#include<stdlib.h>
using namespace std;

class Solution {
public:
    vector<vector<int>> result;
    vector<vector<int>> combine(int n, int k) {
        if(k<=0)
            return result;
        vector<int> nums;
        vector<int> res;
        for(int i=1;i<=n;i++)
            nums.push_back(i);
        getCombine(nums,res,0,k);
        return result;
    }
    void getCombine(vector<int> &nums, vector<int> res, int start, int k){
        if(k == 1){
            for(int i=start;i<nums.size();i++){
                res.push_back(nums[i]);
                result.push_back(res);
                res.pop_back();
            }
        }
        for(int i=start;i<nums.size();i++){
            res.push_back(nums[i]);
            getCombine(nums,res,i+1,k-1);
            res.pop_back();
        }
    }
}; 

Note

To solve this problem, recursion is needed.