python在leecode刷题-第一题

class Solution(object):
    def twoSum(self, nums, target):
        """
        :type nums: List[int] nums=[2,7,11,15],target=9
        :type target: int
        :rtype: List[int]
        """
        hashmap={}
        for index,num in enumerate(nums):
            another_num=target-num
            if another_num in hashmap:
                return [hashmap[another_num],index]
            hashmap[num]=index
        return None

笔记：

1、enumerate用法：这里其实不知道他这个循环nummerate（nums）到底能不能取出来key和value

class Solution(object):
    def reverse(self, x):
        """
        :type x: int
        :rtype: int
        """
        if x<0:
            tmp=-int(str(-x)[::-1])       
        else :
            tmp=int(str(x)[::-1])
        if tmp>=-2**31 and tmp<=2**31-1:
            return tmp
        else:
            return 0

>>> x
-123
>>> str(x)
'-123'
>>> b=str(x)
>>> b[::-1]
'321-'

>>> x
-123
>>> x=-x
>>> x
123
>>> str(x)
'123'
>>> b=str(x)
>>> b
'123'
>>> b[::-1]
'321'
>>>