Leetcode||47. 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],  [2,1,1]]

先排序，在深搜，深搜的时候用pre记录前一个数。

class Solution(object):    def permuteUnique(self, nums):        """        :type nums: List[int]        :rtype: List[List[int]]        """        res = []        nums.sort()        self.dfs(res, [], None, nums)        return res    def dfs(self, res, theList, pre, nums):        if len(nums) == 0:            res.append(list(theList))        pre = None        for i in xrange(len(nums)):            if nums[i] == pre:                continue            theList.append(nums[i])            self.dfs(res, theList, nums[i], nums[:i] + nums[i+1:])            theList.pop()            pre = nums[i]