leetcode77 Combinations

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],
]

class Solution {
public:
    vector<vector<int>> combine(int n, int k) {
        vector<vector<int>> ans;
        vector<int> temp;
        if(k<=n&&k>0)
        {
            dep(n,1,k,temp,ans);
        }
        return ans;
    }
    void dep(int n,int p,int k,vector<int> &temp,vector<vector<int>> &ans)
    {
        if(k==0)
        {
            ans.push_back(temp);
            return;
        }
        if(p<=n)
        {
            temp.push_back(p);
            dep(n,p+1,k-1,temp,ans);
            temp.erase(temp.end()-1);
            dep(n,p+1,k,temp,ans);
        }
        
    }
};