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47. Permutations II

Array Backtracking Sorting

Problem - Permutations II

Medium

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

Solutions

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class Solution:
    def permuteUnique(self, nums: List[int]) -> List[List[int]]:
        nums.sort()
        n = len(nums)
        values = [0] * n
        result = []
        visited = [False] * n

        def dfs(i: int):
            if i == n:
                result.append(values[:])
                return

            for j, val in enumerate(nums):
                if visited[j] or (j and nums[j] == nums[j - 1] and not visited[j - 1]):
                    continue
                visited[j] = True
                values[i] = val
                dfs(i + 1)
                visited[j] = False
        dfs(0)
        return result

Submission Stats:

  • Runtime: 0 ms (100.00%)
  • Memory: 18.3 MB (18.60%)