Permutations ii

class Solution:
    def __init__(self):
        self.path = []
        self.res = []
        self.used = []
    def backtrack(self, nums):
        if len(self.path) == len(nums):
            self.res.append(self.path.copy())
            return None
        usedSet = set()
        for i in range(len(nums)):
            if self.used[i]:
                continue
            if nums[i] in usedSet:
                continue
            self.path.append(nums[i])
            self.used[i] = True
            usedSet.add(nums[i])

            self.backtrack(nums)

            self.used[i] = False
            self.path.pop()

    def permuteUnique(self, nums: List[int]) -> List[List[int]]:
        self.used = [False] * len(nums)
        self.backtrack(nums)
        return self.res

Permutations II

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

 

Example 1:

Input: nums = [1,1,2]
Output:
[[1,1,2],
 [1,2,1],
 [2,1,1]]

Example 2:

Input: nums = [1,2,3]
Output: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]

 

Constraints:

• 1 <= nums.length <= 8
• -10 <= nums[i] <= 10