Given a collection of numbers that might contain duplicates, return all possible unique permutations.
Example:
Input: [1,1,2] Output: [ [1,1,2], [1,2,1], [2,1,1] ]
Time: O(N!)
Space: O(N)
class Solution: def permuteUnique(self, nums: List[int]) -> List[List[int]]: res = [] if nums is None or len(nums) == 0: return res self.dfs(nums, 0, res) return res def dfs(self, nums, level, res): if level == len(nums): res.append(list(nums)) return my_set = set() for i in range(level, len(nums)): if nums[i] not in my_set: my_set.add(nums[i]) nums[i], nums[level] = nums[level], nums[i] self.dfs(nums, level + 1, res) nums[i], nums[level] = nums[level], nums[i]
原文：https://www.cnblogs.com/xuanlu/p/11664671.html