递归练习

#阶乘
def factorial(x):
    if x == 1:
        return 1
    return x * factorial(x-1)

#猴子一天吃一半多一个
def monkey(n):
    if n == 1:
        return 1
    return (monkey(n-1)+1)*2

#斐波那契
def fib(n):
    if n < 1:
        return 1
    return fib(n-1) + fib(n-2)