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