python使用递归解决全排列数字示例

程序员文章站 2022-05-08 20:02:32

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第一种方法：递归

复制代码代码如下:

def perms(elements):
if len(elements) yield elements
else:
for perm in perms(elements[1:]):
for i in range(len(elements)):
yield perm[:i] + elements[0:1] + perm[i:]

for item in list(perms([1, 2, 3,4])):
print item

结果

复制代码代码如下:

[1, 2, 3, 4]
[2, 1, 3, 4]
[2, 3, 1, 4]
[2, 3, 4, 1]
[1, 3, 2, 4]
[3, 1, 2, 4]
[3, 2, 1, 4]
[3, 2, 4, 1]
[1, 3, 4, 2]
[3, 1, 4, 2]
[3, 4, 1, 2]
[3, 4, 2, 1]
[1, 2, 4, 3]
[2, 1, 4, 3]
[2, 4, 1, 3]
[2, 4, 3, 1]
[1, 4, 2, 3]
[4, 1, 2, 3]
[4, 2, 1, 3]
[4, 2, 3, 1]
[1, 4, 3, 2]
[4, 1, 3, 2]
[4, 3, 1, 2]
[4, 3, 2, 1]

第二种方法：python标准库

复制代码代码如下:

import itertools
print list(itertools.permutations([1, 2, 3,4],3))

源代码如下：

复制代码代码如下:

#coding:utf-8
import itertools
print list(itertools.permutations([1, 2, 3,4],3))

def perms(elements):
if len(elements) yield elements
else:
for perm in perms(elements[1:]):
for i in range(len(elements)):
yield perm[:i] + elements[0:1] + perm[i:]

for item in list(perms([1, 2, 3,4])):
print item