递归（正序、倒序）

1、递归倒序打印1-10
def f(n):
print(n)
if n==0 or n==1:
return 
f(n-1)

>>> def f(n):
... print(n)
... if n==0 or n==1:
... return
... f(n-1)
...
>>> f(10)
10
9
8
7
6
5
4
3
2
1
>>>
 

2、递归升序打印1-10
def f(n):
if n<1:
return 
f(n-1)
print(n)

>>>
>>> def f(n):
... if n<1:
... return
... f(n-1)
... print(n)
...
...
>>> f(10)
1
2
3
4
5
6
7
8
9
10
>>>