Leetcode:Combinations 组合

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],
]

void _combination(int n,int k,int start,vector<int> temp,vector<vector<int> >& result){
    if(k==0){
        vector<int>::iterator it = temp.begin();
        for(;it!=temp.end();it++)
            cout<<*it<<" ";
        cout<<endl;
        result.push_back(temp);
    }
    for(int i=start;i<=n;++i){
        temp.push_back(i);
        _combination(n,k-1,i+1,temp,result);
        temp.pop_back();
    }
}
vector<vector<int> > combination(int n,int k){
    vector<int> temp;
    vector<vector<int> > result;
    _combination(n,k,1,temp,result);
　　return result;
}