leetcode #118 in cpp

Given numRows, generate the first numRows of Pascal's triangle.

For example, given numRows = 5,
Return

[
     [1],
    [1,1],
   [1,2,1],
  [1,3,3,1],
 [1,4,6,4,1]
]

Code:

class Solution {
public:
    vector<vector<int>> generate(int numRows) {
        vector<vector<int>> res;
        if(numRows == 0) return res;
        res.push_back(vector<int>{1});
        numRows--;
        while(numRows>0){
            vector<int> member = {1};
            for(int i = 0; i < res.back().size() - 1; i ++){
                member.push_back(res.back()[i] + res.back()[i+1]);
            }
            member.push_back(1);
            res.push_back(member);
            numRows--;
        }
        return res; 
    }
};