[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;        vector<int> num;        dfs(result,num,0,0,n,k);            return result;    }        void dfs(vector<vector<int> > &result, vector<int> &num, int depth, int j,int n, int k)    //从第j个点做深搜        {        if(depth==k)        {            result.push_back(num);             return;                    }                  for(int i=j;i<n;i++)        {            num.push_back(i+1);            dfs(result,num,depth+1,i+1,n,k);            num.pop_back();        }              }};