Easy难度的题目，其实是二项式展开，不需要递归就可以了

Given an integer rowIndex, return the rowIndexth (0-indexed) row of the Pascal's triangle.

In Pascal's triangle, each number is the sum of the two numbers directly above it as shown:

 

Example 1:

Input: rowIndex = 3
Output: [1,3,3,1]

Example 2:

Input: rowIndex = 0
Output: [1]

Example 3:

Input: rowIndex = 1
Output: [1,1]

Constraints:

• 0 <= rowIndex <= 33

  class Solution:def fraction(self, n):product = 1if n==0:return 1else:for i in range(n):product = product*(i+1)return productdef Pr(self, n, m):return self.fraction(n)/(self.fraction(m)*self.fraction(n-m))def getRow(self, rowIndex):output = []for i in range(rowIndex+1):output.append(int(self.Pr(rowIndex,i)))return output