[LeetCode]题解（python）：118 Pascal's Triangle

题目来源

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https://leetcode.com/problems/pascals-triangle/

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]
]

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题意分析

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Input:integer

Output:帕斯卡三角

Conditions:帕斯卡三角数值的规律

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题目思路

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注意帕斯卡三角中，除了首尾，其他值为上一层的两个邻值的和

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AC代码（Python）

class Solution(object):
    def generate(self, numRows):
        """
        :type numRows: int
        :rtype: List[List[int]]
        """
        ans = []
        for i in range(numRows):
            this = []
            for j in range(i+1):
                this.append(1)
            if i > 1:
                for x in range(i - 1):
                    this[x+1] = ans[i-1][x] + ans[i-1][x+1]
            print this
            ans.append(this)
        return ans