題目描述：

            給定一組不含重復(fù)元素的整數(shù)數(shù)組?nums，返回該數(shù)組所有可能的子集（冪集）。

說明：解集不能包含重復(fù)的子集。

示例:

輸入: nums = [1,2,3]
輸出:
[
  [3],
? [1],
? [2],
? [1,2,3],
? [1,3],
? [2,3],
? [1,2],
? []
]

          

SOLUTION1:迭代法

比較常規(guī)的迭代法思路，循環(huán)nums數(shù)組，每次訪問其中元素，將其轉(zhuǎn)化為數(shù)組并加到result二維數(shù)組當(dāng)中。

CODE:

            
              class Solution:
    def subsets(self,nums):
        '''
        nums:list[int]
        return:list[list[int]]
        '''
        if len(nums) == 0:
            return [[]]
        result = [[]]
        for i in nums:
            result = result + [[i] + num for num in result]
        return result
    
        

            
          

SOLUTION2:遞歸法

CODE:

            
              class Solution:
    def subsets(self,nums):
        if len(nums) == 0:
            return [[]]
        result = []
        def helper(i,tmp):
            result.append(tmp)
            for j in range(i,len(nums)):
                helper(j+1,tmp+nums[j])
        helper(0,[])
        return result
            
          

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