题目

image.png
image.png

思路

  1. class Solution:
  2.     def generate(self, numRows: int) -> List[List[int]]:
  3.         ans = []
  4.         for num in range(numRows):
  5.             row = [None for _ in range(num+1)]
  6.             row[0], row[-1] = 1, 1
  7.             for j in range(1, num):
  8.                 row[j] = last[j - 1] + last[j]
  9.             last = row
  10.             ans.append(row)
  11.         return ans