90. Subsets II

Given a collection of integers that might contain duplicates, nums, return all possible subsets (the power set).

Note: The solution set must not contain duplicate subsets.

Example:

Input: [1,2,2]
Output:
[
  [2],
  [1],
  [1,2,2],
  [2,2],
  [1,2],
  []
]

Code:

class Solution(object):
    def subsetsWithDup(self, nums):
        """
        :type nums: List[int]
        :rtype: List[List[int]]
        """
        res = []
        nums.sort()
        self.dfs(nums, 0, [], res)
        return res
    def dfs(self, nums, index, path, res):
        res.append(path)
        for i in range(index, len(nums)):
            if i > index and nums[i] == nums[i-1]:
                continue
            self.dfs(nums, i+1, path+[nums[i]], res)