题目
Given a non-negative index k where k ≤ 33, return the kth index row of the Pascal’s triangle.
Note that the row index starts from 0.
解题思路
对于每一行，从后向前求，就不需要额外空间了
代码
class Solution:
def getRow(self, rowIndex: int) -> List[int]:
res = [1]
for i in range(rowIndex):
for j in range(i, 0, -1):
res[j] += res[j - 1]
res.append(1)
return res
