生成数组的所有子集

Question

我正在努力生成数组的所有可能子集。我正在研究递归解决方案，其中我维护一个索引，我在每一步都递增。递增索引后，我弹出最后一个元素。我不明白为什么数组中的最后一个元素会重复。

class Solution(object):
  def subsets(self, nums):
    """
    :type nums: List[int]
    :rtype: List[List[int]]
    """
    # You need to keep track of a list of all the subarrays, the current subarray, the index and the original array
    return self.helper(nums, 0, [], [])


  def helper(self, nums, index, fullSol, curr):
    fullSol.append(list(curr)) # add this current array to the list of all subarrays
    print(fullSol)

    # Iterate through the indices
    for i in range(index, len(nums)): 
        curr.append(nums[index]) # add the next element to the current list
        self.helper(nums, i+1, fullSol, curr) # increment the index
        curr = curr[:-1] # remove the last element from the current subarray