忘事儿的菲芸
"""
使用map和reduce实现阶乘求和 x!+(x-1)!+(x-2)!+...+1!
x! = x * (x-1) * (x-2) * ... * 1
0! = 1
"""
# coding = utf-8
def factorial(n):
return reduce(lambda x,y:x*y, range(1, n+1))
def factorial_sum(n):
""" 阶乘求和 """
if n == 0:
return 1
else:
a = map(lambda x:factorial(x), range(1, n+1))
b = reduce(lambda x,y:x+y, a)
return b
print factorial_sum(5)
153
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