[LeetCode]题解（python）：046-Permutations

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题目来源

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https://leetcode.com/problems/permutations/

Given a collection of distinct 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].

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题意分析

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Input: a list

Output: a permutations

Conditions:全排列

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题目思路

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递归解决。注意到python取list的若干位很方便，分片~然后仔细发现不单是全排序，而且还是字典序（因为每一次遍历都是从小到大的，遍历顺序取决~）

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AC代码（Python）

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 class Solution(object):
     def permute(self, nums):
         """
         :type nums: List[int]
         :rtype: List[List[int]]
         """
         if len(nums) == 1:
             return [nums]
         res = []
         for i in range(len(nums)):
             for j in self.permute(nums[:i] + nums[i+1:]):
                 res.append([nums[i]] + j)
         return res