LeetCode OJ 系列之78 Subsets --Python

Problem:

Given a set of distinct integers, nums, return all possible subsets.

Note:

Elements in a subset must be in non-descending order.
The solution set must not contain duplicate subsets.

For example,

If nums = 

[1,2,3]

, a solution
is:

[
[3],
[1],
[2],
[1,2,3],
[1,3],
[2,3],
[1,2],
[]
]

Answer:

class Solution(object):

def subsets(self, nums):
"""
:type nums: List[int]
:rtype: List[List[int]]
"""
result = self.subset_func(nums)
for line in result:
line.sort()
return result

def subset_func(self,nums):
if len(nums)==0:
return [[]]
if len(nums)==1:
return [[],nums]
first = nums[0]
tmp_nums = nums[1:]
tmp_result = self.subset_func(tmp_nums)
result = []
for key in tmp_result:
result.append(key)
tmp = list(key)
tmp.append(first)
result.append(tmp)
return result

Analysis:

利用动态规划的思想，当想要为集合A添加一个新的元素x时，得到的新集合A+1，必然是由下面两部分组成：

集合A里所有的项
集合A里每一项添加新的元素x之后形成的新项。