47. 全排列 II

class Solution:
    def permuteUnique(self, nums: List[int]) -> List[List[int]]:
        nums.sort()
        res = []
        def help(tmp,nums):
            if not nums:
                res.append(tmp)
                return 
            for i in range(len(nums)):
                # 剪枝  避免出现重复的解
                if i!=0 and nums[i-1]==nums[i]:
                    continue
                help(tmp+[nums[i]],nums[:i]+nums[i+1:])
        help([],nums)
        return res