344. Reverse String

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"]

思路：替换头尾字符

代码:python3

class Solution:
    def reverseString(self, s: List[str]) -> None:
        """
        Do not return anything, modify s in-place instead.
        """
        if len(s)==0:
            return
        low=0
        high=len(s)-1
        for index,value in enumerate(s):
            if index<high/2:
                s[index],s[high-index]=s[high-index],s[index]