```
func generate(_ numRows: Int) -> [[Int]] {
var ans:[[Int]] = [[1], [1,1]]
if numRows <= 0 { return [] }
if numRows == 1 { return [[1]] }
for i in 1..<numRows-1{
var temp:[Int] = [1,1]
for j in 0..<ans[i].count{
if j+1<ans[i].count{
temp.insert(ans[i][j] + ans[i][j+1], at: 1)
}
}
ans.append(temp)
}
return ans
}
```