# 20190108 use of recursive function to realize the use of basic recursive functions such as finding the greatest common divisor

1. Given a = [1,2,[3,4,[5,6,7,[8,9,[10,11]]]], print output is required: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11

Use the recursive function to traverse A. when the value of a is list, continue to call the recursive function, and take values one by one

```def iter_list(l):
for i in l:
if isinstance(i,list):
iter_list(i)
#The elements in the list passed in before are list Call the recursive function
else:
print(i,end =' ')
iter_list(a)```

2. Make the result a list based on the first question

```#Method 1
def iter_list(l,result=[]):
#result Is the default parameter, which is used when no value is passed result=[],Use the value passed in when passing the value
for i in l:
if isinstance(i,list):
iter_list2(i,result)
else:
result.append(i)
return result
print(iter_list(a))
#Method 2
def iter_list2(l,result):
for i in l:
if isinstance(i,list):
iter_list2(i,result)
else:
result.append(i)
return result
result =[]
print(iter_list2(a,result))```

3. Write a method recursively to output n,n-1....10, 9, 8... 1 to 0 end

```#algorithm:Print each number, exit recursion when the number is less than 0
def output_num(n):
print(n)
if n>0:
output_num(n-1)
else:
print('----')
output_num(5)```

4. Using recursive function to write a method to find the maximum co constraint

#Algorithm: use the rolling phase division method for the maximum common divisor
Find (319377):
∵ 319 ÷ 377 = 0 (balance 319)
∴(319，377)=(377，319)；
∵ 377 ÷ 319 = 1 (remaining 58)
∴(377，319)=(319，58)；
∵ 319 ÷ 58 = 5 (remaining 29)
∴ (319，58)=(58，29)；
∵ 58 ÷ 29 = 2 (remaining 0)
∴ (58，29)= 29；
∴ (319，377)=29

```def find_max_common_divisor(a,b):
if a<b:
a,b = b,a
print(a,b)
#ensure a>b
if a%b!=0:
print('a%b Branch taken')
temp = b
b = a%b
a = temp
print(a,b)
return find_max_common_divisor(a,b)
#return There is a short-circuit effect. The following statements will not be executed
else:
return b
print(find_max_common_divisor(319,377))```

Tags: Python less

Posted on Wed, 04 Dec 2019 13:08:24 -0500 by minifairy