class Solution {
public:
vector > generate(int numRows) {
vector > ret;
if (numRows == 0) return ret;
vector m;
m.push_back(1);
ret.push_back(m);
if (numRows == 1) return ret;
for (int i = 2; i <= numRows; ++i) {
m.clear();
m.push_back(1);
for (int j = 1; j < i - 1; ++j) m.push_back(ret[i - 2][j] + ret[i - 2][j - 1]);
m.push_back(1);
ret.push_back(m);
}
return ret;
}
};