例题

1. 子集

image.png
代码
Python代码：

  1. def subsets(self, nums: List[int]) -> List[List[int]]:
  2.         def generate(i, nums, path, res):
  3.             if i == len(nums):
  4.                 return
  5.             path.append(nums[i])
  6.             # if tuple(path) not in s:
  7.             res.append(path.copy())
  8.                 # s.add(tuple(path))
  9.             generate(i+1, nums, path, res)
  10.             path.pop()
  11.             generate(i+1, nums, path, res)
  13.         path = []
  14.         res = [[]]
  15.         s = set()
  16.         generate(0, nums, path, res)
  17.         return res

二进制：

  1. def subsets(self, nums: List[int]) -> List[List[int]]:
  2.         n = len(nums)
  3.         output = []
  5.         for i in range(2**n, 2**(n + 1)):
  6.             # generate bitmask, from 0..00 to 1..11
  7.             bitmask = bin(i)[3:]
  9.             # append subset corresponding to that bitmask
  10.             output.append([nums[j] for j in range(n) if bitmask[j] == '1'])
  12.         return output

2. 子集2

image.png
代码 

  1. class Solution:
  2.     def subsetsWithDup(self, nums: List[int]) -> List[List[int]]:
  3.         nums.sort()
  4.         subset, result = [], [[]]
  5.         self.DFS(nums, 0, len(nums), subset, result)
  6.         return result
  8.     def DFS(self, nums, start, end, subset, result):
  9.         for i in range(start, end):
  10.             if i > start and nums[i] == nums[i-1]:
  11.                 continue
  12.             subset.append(nums[i])
  13.             result.append(subset[:])
  14.             self.DFS(nums, i+1, end, subset, result)
  15.             subset.pop()