動機
46的follow-up
Problem
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
Sol
在同一層不要展開已經展開過的數字
class Solution:
def permuteUnique(self, nums: List[int]) -> List[List[int]]:
def dfs(nums,acc):
if not nums:
return [acc]
else:
seen,ret = set(), []
for k in range(len(nums)):
if nums[k] not in seen:
seen.add(nums[k])
ret += dfs(nums[:k]+nums[k+1:],acc+[nums[k]])
return ret
return dfs(nums,[])