python递归

求阶乘

>>> def recursion(x,y):
	if x != 1:
		y *= x
		x -= 1
		recursion(x,y)
	else:
		print(y)

斐波那契数列

>>> def feibo(n):
	if n == 1:
		return 1
	elif n == 2:
		return 1
	else:
		return feibo(n-1) + feibo(n-2)
#迭代实现方法
>>> def feibo1(n):
	if n == 1:
		return 1
	if n == 2:
		return 1
	x = 1
	y = 1
	for i in range(n-2):
		sum1 = x + y
		x = y
		y = sum1
	return sum1