题目信息

• 链接: reverse-string

• Write a function that reverses a string. The input string is given as an array of characters s.

  You must do this by modifying the input array in-place with O(1) extra memory.

  Example 1:

  Input: s = ["h","e","l","l","o"]
  Output: ["o","l","l","e","h"]
  
  

  Example 2:

  Input: s = ["H","a","n","n","a","h"]
  Output: ["h","a","n","n","a","H"]
  
  

  Constraints:

  • 1 <= s.length <= 10<sup>5</sup>
  • s[i] is a printable ascii character.

• 描述:

  • 编写一个函数，其作用是将输入的字符串反转过来。输入字符串以字符数组 s 的形式给出。
  • 不要给另外的数组分配额外的空间，你必须原地修改输入数组、使用 O(1) 的额外空间解决这一问题

解题思路

• 使用首尾双指针，头尾交换元素，left右移，right左移，直到left、right相遇

代码

 class Solution:
     def reverseString(self, s: List[str]) -> None:
   	  """
   	  Do not return anything, modify s in-place instead.
   	  """
   	  left = 0
   	  right = len(s)-1
   	  while left < right:
   		  # swap l, r
   		  temp = s[left]
   		  s[left] = s[right]
   		  s[right] = temp
   		  # move left, right
   		  left += 1
   		  right -= 1