90. Subsets II

https://leetcode.com/problems/subsets-ii/#/description

Given a collection of integers that might contain duplicates, nums, return all possible subsets.

Note: The solution set must not contain duplicate subsets.

For example,
If nums = [1,2,2], a solution is:

[
  [2],
  [1],
  [1,2,2],
  [2,2],
  [1,2],
  []
]

Sol 1:

Iteration.

Sort first.

class Solution(object):
    def subsetsWithDup(self, nums):
        """
        :type nums: List[int]
        :rtype: List[List[int]]
        """
        
        # iterately 
        res = [[]]
        nums.sort()
        for num in nums:
            res += [item + [num] for item in res if item + [num] not in res]
        return res

Sol 2:

DFS.

class Solution(object):
    def subsetsWithDup(self, nums):
        """
        :type nums: List[int]
        :rtype: List[List[int]]
        """
        
        # DFS
        
        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)