python 递归函数

斐波那契数列

1,1,2,3,5,8   #fib(6) = fib(5) + fib(4)

def fib(n):
    if n == 1 or n==2:
        return 1
    return fib(n-1) + fib(n-2)
print(fib(50))

 另一种方法

def fib(n,a=1,b=1):
    if n==1 : return a
    return fib(n-1,b,a+b)

print(fib(5))

 用生成器

def fib(n):
    prev,curr = 0,1
    while n > 0:
        n -= 1
        yield curr
        prev,curr = curr,curr + prev

print([i for i in fib(10)])

阶乘

3！= 3*2*1

def fac(n):
    if n == 1 :
        return 1
    return n * fac(n-1)

print(fac(100))