class Solution { public: vector<vector<int>> generate(int numRows) { vector<vector<int>> vv; vector<int> v_arr[numRows+1]; if( numRows <= 0) return vv; v_arr[1].push_back(1); vv.push_back(v_arr[1]); if(numRows == 1) return vv; for(int row=2;row<=numRows;row++){ v_arr[row].push_back(1); // 1 at begin int pre_len = v_arr[row-1].size(); for(int i=0;i<pre_len-1;i++){ v_arr[row].push_back(v_arr[row-1][i]+v_arr[row-1][i+1]); } v_arr[row].push_back(1); //1 at end vv.push_back(v_arr[row]); } return vv; } };