【LeetCode】Reverse Words in a String

字符串操作：单词反转与空格处理

最新推荐文章于 2024-01-04 11:20:32 发布

哎-哭泣的鱼

最新推荐文章于 2024-01-04 11:20:32 发布

阅读量1.1k

点赞数

CC 4.0 BY-SA版权

分类专栏： LeetCode 字符串算法 LeetCode解题报告

本文链接：https://blog.youkuaiyun.com/u013027996/article/details/20723361

算法同时被 3 个专栏收录

209 篇文章

订阅专栏

LeetCode

133 篇文章

订阅专栏

LeetCode解题报告

121 篇文章

订阅专栏

本文介绍如何在给定输入字符串中，通过算法实现单词级别的反转，并且处理字符串中的空格，确保反转后的字符串符合指定条件，即去除前后空格、减少内部多余空格、并保持单词顺序不变。

Reverse Words in a String
Total Accepted: 357 Total Submissions: 2355 My Submissions
Given an input string, reverse the string word by word.
For example,
Given s = "the sky is blue",
return "blue is sky the".
Clarification:
What constitutes a word?
A sequence of non-space characters constitutes a word.
Could the input string contain leading or trailing spaces?
Yes. However, your reversed string should not contain leading or trailing spaces.
How about multiple spaces between two words?
Reduce them to a single space in the reversed string.
【解题思路】
1、扫描字符串，按照字符去处理，遇到空格则之前为一个完整的字符串。全部放入list，最后逆序返回。
2、替换掉字符串前后的空白，将中间的多个空格替换为一个，按照正则空格分隔为字符串，逆序返回。

Java AC 1

public class Solution {
    public String reverseWords(String s) {
        if(s == null || "".equals(s.trim())){
            return s.trim();
        }
        List<String> list = new ArrayList<String>();
        s = s.trim();
        StringBuffer sb = new StringBuffer();
        int i = 0;
        int len = s.length();
        while(i < len){
            sb = new StringBuffer();
            while(i < len && s.charAt(i) != ' '){
            	sb.append(String.valueOf(s.charAt(i)));
                i++;
            }
            while(i < len && s.charAt(i) == ' '){
                i++;
            }
            list.add(sb.toString());
        }
        int size = list.size();
        sb = new StringBuffer();
        for(i = size-1; i >= 0; i--){
            sb.append(list.get(i)+" ");
        }
        return sb.toString().trim();
    }
}

update 2014-06-10

Java AC 2

public class Solution {
    public String reverseWords(String s) {
		s = s.trim().replaceAll("[ ]+", " ");
		String sArr[] = s.split(java.util.regex.Pattern.quote(" "));
		StringBuffer sb = new StringBuffer();
		int len = sArr.length;
		for (int i = len - 1; i >= 0; i--) {
			sb.append(sArr[i] + " ");
		}
		return sb.toString().trim();
	}
}

Python AC 2

class Solution:
    # @param s, a string
    # @return a string
    def reverseWords(self, s):
        sArr = s.strip().split()
        slen = len(sArr)
        news = ''
        for i in range(slen-1, -1, -1):
            news += sArr[i]
            news += ' '
        return news.strip()