```
def getRow(self, rowIndex):
ret = [1] * (rowIndex + 1)
comb_next = lambda x, m, n: x * (m - n + 1) // n
for n in range(1, rowIndex // 2 + 1):
ret[n] = ret[-n-1] = comb_next(ret[n-1], rowIndex, n)
return ret
```

I thought formula would be faster, but it didn't.

Why's that?