Leetcode: Combinations

class Solution {public:    vector<vector<int> > combine(int n, int k) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        vector<vector<int> > result;        for(int i=1;i<=n;++i){            result.push_back(vector<int>());            result.back().push_back(i);        }        for(int i=1;i<k;++i){            result=getNext(n,result);        }        return result;    }        vector<vector<int> > getNext(int n,vector<vector<int> >& current){        vector<vector<int> > result;        for(int i=0;i<current.size();++i){            for(int j=current[i].back()+1;j<=n;++j){                result.push_back(current[i]);                result.back().push_back(j);            }        }        return result;    }    };