题目描述：
Write a function that takes a string as input and returns the string reversed.
Example:
Given s = "hello", return "olleh".
解题思路：
见代码。
代码如下：
class Solution(object):
def reverseString(self, s):
"""
:type s: str
:rtype: str
"""
t = list(s)
l = len(t)
for i, j in zip(range(l - 1, 0, -1), range(l // 2)):
t[i], t[j] = t[j], t[i] return ''.join(t)