problem address
Write a function that reverses a string. The input string is given as an array of characters char[]. Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory. You may assume all the characters consist of printable ascii characters. Example 1: Input: ["h","e","l","l","o"] Output: ["o","l","l","e","h"] Example 2: Input: ["H","a","n","n","a","h"] Output: ["h","a","n","n","a","H"]这里注意是字符数组，python里面是字符串列表。 可以用s.reverse()直接反转
class Solution: def reverseString(self, s): """ Do not return anything, modify s in-place instead. """ beg = 0 end = len(s) - 1 while beg < end: s[beg], s[end] = s[end], s[beg] beg += 1 end -= 1