leetcode78

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78. Subsets

Given a set of distinct integers, nums, return all possible subsets (the power set).

Note: The solution set must not contain duplicate subsets.

Example:

Input: nums = [1,2,3]
Output:
[
[3],
[1],
[2],
[1,2,3],
[1,3],
[2,3],
[1,2],
[]
]

Idea

classical dfs problem

Code

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class Solution(object):
    def subsets(self, nums):
        """
        :type nums: List[int]
        :rtype: List[List[int]]
        """
        self.res = []
        if not nums:
            return self.res
        self.dfs([], 0, nums)
        return self.res
        
    # return all the subset while start from pos in nums
    def dfs(self, subset, pos, nums):
        if pos > len(nums):
            return
        
        self.res.append(list(subset))
        for i in range(pos, len(nums)):
            subset.append(nums[i])
            self.dfs(subset, i+1, nums)
            subset.pop()