递归和回溯_leetcode78-经典的子集

class Solution(object):
    def subsets(self, nums):
        """
 :type nums: List[int]
 :rtype: List[List[int]]
 """

 self.res = []
 self.res.append([])
 # for i in range(len(nums)):
 self.generateSub(nums,0,[])
 # print self.res

 return self.res


 def generateSub(self,nums,start,ans):

 if ans:
 self.res.append(ans[0:])


 for i in range(start,len(nums)):
 ans.append(nums[i])
 self.generateSub(nums,i+1,ans)
 ans.pop()




s = Solution()

nums = [1,2,3]

s.subsets(nums)