class Solution {
public:
    vector<vector<int>> generate(int numRows) {
        vector<vector<int>> ret(numRows,vector<int>(0));
        for(int i = 0; i< numRows; ++i) {
            ret[i].push_back(1);
            for(int j =1;j<i;++j) {
                ret[i].push_back(ret[i-1][j-1]+ret[i-1][j]);
            }
            if( i > 0 ) {
                ret[i].push_back(1);
            }
        }
        return ret;

    }
};