[119]Pascal's Triangle II

Given an index k, return the kth row of the Pascal's triangle.

For example, given k = 3, Return [1,3,3,1].

Note: Could you optimize your algorithm to use only O(k) extra space?

思路

迭代，每次存下当前行的元素，通过当前行得到下一行。

Code

Python

class Solution(object):
    def getRow(self, rowIndex):
        row = [1]
        for i in range(rowIndex):
            row = [u+v for u,v in zip(row+[0], [0]+row)]
        return row