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QiShunwang

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【杨辉三角妙解】python用生成器计算杨辉三角

2021/3/21 10:43:52   来源:

【题目来源】:廖雪峰老师的python教程
【问题】:
在这里插入图片描述
【解答】:

# -*- coding: utf-8 -*-
def triangles():
    L = [1]
    while True:
        yield L[:]	#用生成器每次取一行的数据,通过现有的一行计算下一行
        L.append(0)	#本行补0,这个操作太妙了!
        L = [L[i] + L[i - 1] for i in range(len(L))]	#求新的一行

测试程序

# 期待输出:
# [1]
# [1, 1]
# [1, 2, 1]
# [1, 3, 3, 1]
# [1, 4, 6, 4, 1]
# [1, 5, 10, 10, 5, 1]
# [1, 6, 15, 20, 15, 6, 1]
# [1, 7, 21, 35, 35, 21, 7, 1]
# [1, 8, 28, 56, 70, 56, 28, 8, 1]
# [1, 9, 36, 84, 126, 126, 84, 36, 9, 1]
n = 0
results = []
for t in triangles():
    results.append(t)
    n = n + 1
    if n == 10:
        break

for t in results:
    print(t)

if results == [
    [1],
    [1, 1],
    [1, 2, 1],
    [1, 3, 3, 1],
    [1, 4, 6, 4, 1],
    [1, 5, 10, 10, 5, 1],
    [1, 6, 15, 20, 15, 6, 1],
    [1, 7, 21, 35, 35, 21, 7, 1],
    [1, 8, 28, 56, 70, 56, 28, 8, 1],
    [1, 9, 36, 84, 126, 126, 84, 36, 9, 1]
]:
    print('测试通过!')
else:
    print('测试失败!')