LeetCode: 344. Reverse String-简单-Python+Java

发布时间：2020-12-20 10:42:44 所属栏目：Python 来源：网络整理

导读：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

  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","o"] Output: ["o","h"]  

 
 Example 2: 

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

?

 
 解题思路： 

  用两个指针，分别指向头和尾，互相交换值（java需要一个temp变量来保存值 O(1)），头指针向后移动，尾指针向前移动，直到头指针大于等于尾部指针 

  时间 o（n/2） 空间o（1） 

?

 
 Java: 

 
  class Solution {
    public void reverseString(char[] s) {
        int start = 0;
        int end = s.length-1;
        while(start<end){
            char tmp = s[end];
            s[end--] = s[start];
            s[start++] = tmp;
        }
    }
}
 
 
?Python：

 
  class Solution(object):
    def reverseString(self,s):
        """
        :type s: List[str]
        :rtype: None Do not return anything,modify s in-place instead.
        """
        start,end = 0,len(s)-1
        while start < end:
            s[start],s[end] = s[end],s[start];
            start += 1
            end -= 1 
 

（编辑：李大同）

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