LeetCode——Pascal's 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]

]

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

杨辉三角，先把两遍的值设为1，然后算中间的就是上一层的两个数相加，算当前层的时候，上一层下标一定是从0开始一直加到最后一个。

Python代码

class PascalsTriangle:

    def generate(self, numRows):

        res = []

        for i in range(1, numRows+1):

            tem = [0 for x in range(i)]

            if i == 1:

                tem[0] = 1

                # print(tem[0])

                res.append(tem)

            else:

                pos = 0

                for j in range(1, i+1):

                    if j == 1:

                        tem[0] = 1

                    elif j == i:

                        tem[j - 1] = 1

                    else:

                        tem[j-1] = res[i-2][pos] + res[i-2][pos+1]

                        pos += 1

                res.append(tem)

        return res





p = PascalsTriangle()

p.generate(5)