[leetcode]Permutations @ Python

原题地址：https://oj.leetcode.com/problems/permutations/

题意：

Given a collection of numbers, return all possible permutations.

For example,

[1,2,3]

have the following permutations:

[1,2,3]

,

[1,3,2]

,

[2,1,3]

,

[2,3,1]

,

[3,1,2]

, and

[3,2,1]

.

解题思路：穷举一个集合的全排列。这个就是python递归巧妙的使用了。

代码：

class Solution:
# @param num, a list of integer
# @return a list of lists of integers
def permute(self, num):
if len(num) == 0: return []
if len(num) == 1: return [num]
res = []
for i in range(len(num)):
for j in self.permute(num[:i] + num[i+1:]):
res.append([num[i]] + j)
return res