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
SOLUTION:
class Solution:
def permuteUnique(self, nums: List[int]) -> List[List[int]]:
n = len(nums)
ctr = {}
for num in nums:
ctr[num] = ctr.get(num, 0) + 1
nums = set(nums)
paths = [([num], { **ctr, num: ctr[num] - 1 }, 1) for num in nums]
while paths[0][2] < n:
curr, currCtr, l = paths.pop(0)
for num in nums:
if currCtr[num] > 0:
paths.append((curr + [num], { **currCtr, num: currCtr[num] - 1 }, l + 1))
return [perm[0] for perm in paths]
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