[LeetCode]题解（python）：047-Permutations II

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题目来源

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

Given a collection of numbers that might contain duplicates, return all possible unique permutations.

For example,
[1,1,2] have the following unique permutations:
[1,1,2], [1,2,1], and [2,1,1].

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题意分析
Input:list

Output:permutations

Conditions:跟上题类似，但是会有重复的元素

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题目思路

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直接用上题的做法，首先先排序，然后再遍历的时候用一个pre记录先前位置，如果当前位置与pre相同则跳过

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AC代码（Python）

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class Solution(object):
    def permuteUnique(self, nums):
        """
        :type nums: List[int]
        :rtype: List[List[int]]
        """
        nums.sort()
        if len(nums) == 1:
            return [nums]
        res = []
        pre = None
        for i in range(len(nums)):
            if nums[i] == pre:
                continue
            pre = nums[i]
            for j in self.permuteUnique(nums[:i] + nums[i+1:]):
                res.append([nums[i]] + j)
        return res