题目简述：

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]

]

解题思路：

很简单的问题，只要把两头的一拿出来，中间就是两个数相加了。

class Solution:

    # @return a list of lists of integers

    def generate(self, numRows):

        if numRows == 0:

            return []

        res = [[1]]

        for i in range(1,numRows):

            t = [1]

            pre = res[-1]

            for i in range(len(pre)-1):

                t.append(pre[i]+pre[i+1])

            t.append(1)

            res.append(t)

        return res