[leetcode: Python] 118.Pascal's Triangle

题目：
Given numRows, generate the first numRows of Pascal’s triangle.

For example, given numRows = 5,
Return

[     [1],    [1,1],   [1,2,1],  [1,3,3,1], [1,4,6,4,1]]

方法一：性能39ms

class Solution:      def generate(self, numRows):        if numRows == 0:            return []        ret = []        for i in range(numRows):            ret.append([1])            for j in range(1, i + 1):                if j == i:                    ret[i].append(1)                else:                    ret[i].append(ret[i-1][j-1]+ret[i-1][j])        return ret

as far as i know, 这个性能挺好的了。暂时没发现比这更好的方法。