Leetcode Reverse Words in a String II

最新推荐文章于 2025-09-12 18:08:49 发布

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原文链接：http://www.cnblogs.com/anne-vista/p/4868723.html

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#java

本文介绍了一种通过两次反转实现字符串单词反转的方法，并提供了详细的Java代码实现。该算法首先整体反转整个字符串，然后逐个反转每个单词，实现了在原地操作且不使用额外空间的要求。

Given an input string, reverse the string word by word. A word is defined as a sequence of non-space characters.

The input string does not contain leading or trailing spaces and the words are always separated by a single space.

For example,
Given s = "the sky is blue",
return "blue is sky the".

Could you do it in-place without allocating extra space?

解题思路：

和Leetcode Rotate Array 思路一样。

（1）reverse the whole array

（2）reverse each subarray seperated by ' '

Java code:

public class Solution {
    public void reverseWords(char[] s) {
        reverse(s, 0, s.length-1);
        int start = 0;
        for(int i = 0; i< s.length; i++){
            if(s[i] == ' '){
                reverse(s, start, i-1);
                start = i+1;
            }
        }
        reverse(s, start, s.length-1); 
    }
    
    public void reverse(char[] s, int l, int r){
        while(l < r){
            char temp = s[l];
            s[l] = s[r];
            s[r] = temp;
            l++;
            r--;
        }
    }
}