Question

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],
  []
]

Solution

class Solution:
    def subsets(self, nums):
        """
        :type nums: List[int]
        :rtype: List[List[int]]
        """      
        res = list()
        res.append([])
        self.backtracking(res, nums, [], -1, len(nums))
        return res

    def backtracking(self, res, nums, partial, i, length):
        i += 1
        while i < length:
            new_partial = partial + [nums[i]]
            res.append(new_partial)
            self.backtracking(res, nums, new_partial, i, length)
            i += 1