leetcode 118 杨辉三角 python

杨辉三角  一开始自己使用的方法
 1 class Solution:
 2     def generate(self, numRows):
 3         """
 4         :type numRows: int
 5         :rtype: List[List[int]]
 6         """
 7         if numRows == 0:
 8             return []
 9         elif numRows == 1:
10             return [[1]]
11         elif numRows == 2:
12             return [[1], [1, 1]]
13         else:
14             triangle = [[1],[1,1]]
15             for i in range(2, numRows):
16                 triangle.append([])
17                 triangle[i].append(1)
18                 for j in range(1, i):
19                     triangle[i].append(triangle[i - 1][j - 1] + triangle[i - 1][j])
20                 triangle[i].append(1)
21             return triangle
了解了python的生成器后重写了一下

class Solution:
    def generate(self, numRows):
        """
        :type numRows: int
        :rtype: List[List[int]]
        """
        def rowGenerator():
            row = [1]
            while True:
                yield(row)
                row = [1] + [row[k] + row[k + 1] for k in range(len(row) - 1)] + [1]
            
        listn = rowGenerator()
        a = []
        while numRows > 0:
            a.append(next(listn))
            numRows -= 1
        return a