Project Notes

Reverse Words in a String

4 min read

Nav: << previous: 150.逆波兰表达式求值 | next: 152.乘积最大子数组 >>

Description

tab: English
 
<p>Given an input string <code>s</code>, reverse the order of the <strong>words</strong>.</p>
 
<p>A <strong>word</strong> is defined as a sequence of non-space characters. The <strong>words</strong> in <code>s</code> will be separated by at least one space.</p>
 
<p>Return <em>a string of the words in reverse order concatenated by a single space.</em></p>
 
<p><b>Note</b> that <code>s</code> may contain leading or trailing spaces or multiple spaces between two words. The returned string should only have a single space separating the words. Do not include any extra spaces.</p>
 
<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
 
<pre>
<strong>Input:</strong> s = &quot;the sky is blue&quot;
<strong>Output:</strong> &quot;blue is sky the&quot;
</pre>
 
<p><strong class="example">Example 2:</strong></p>
 
<pre>
<strong>Input:</strong> s = &quot;  hello world  &quot;
<strong>Output:</strong> &quot;world hello&quot;
<strong>Explanation:</strong> Your reversed string should not contain leading or trailing spaces.
</pre>
 
<p><strong class="example">Example 3:</strong></p>
 
<pre>
<strong>Input:</strong> s = &quot;a good   example&quot;
<strong>Output:</strong> &quot;example good a&quot;
<strong>Explanation:</strong> You need to reduce multiple spaces between two words to a single space in the reversed string.
</pre>
 
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>
 
<ul>
	<li><code>1 &lt;= s.length &lt;= 10<sup>4</sup></code></li>
	<li><code>s</code> contains English letters (upper-case and lower-case), digits, and spaces <code>&#39; &#39;</code>.</li>
	<li>There is <strong>at least one</strong> word in <code>s</code>.</li>
</ul>
 
<p>&nbsp;</p>
<p><b data-stringify-type="bold">Follow-up:&nbsp;</b>If the string data type is mutable in your language, can&nbsp;you solve it&nbsp;<b data-stringify-type="bold">in-place</b>&nbsp;with&nbsp;<code data-stringify-type="code">O(1)</code>&nbsp;extra space?</p>
 
 
 
---
 
[submissions](https://leetcode.com/problems/reverse-words-in-a-string/submissions/) | [solutions](https://leetcode.com/problems/reverse-words-in-a-string/solutions/)
 
 
tab: 中文
 
<p>给你一个字符串 <code>s</code> ，请你反转字符串中 <strong>单词</strong> 的顺序。</p>
 
<p><strong>单词</strong> 是由非空格字符组成的字符串。<code>s</code> 中使用至少一个空格将字符串中的 <strong>单词</strong> 分隔开。</p>
 
<p>返回 <strong>单词</strong> 顺序颠倒且 <strong>单词</strong> 之间用单个空格连接的结果字符串。</p>
 
<p><strong>注意：</strong>输入字符串 <code>s</code>中可能会存在前导空格、尾随空格或者单词间的多个空格。返回的结果字符串中，单词间应当仅用单个空格分隔，且不包含任何额外的空格。</p>
 
<p>&nbsp;</p>
 
<p><strong>示例 1：</strong></p>
 
<pre>
<strong>输入：</strong>s = "the sky is blue"
<strong>输出：</strong>"blue is sky the"
</pre>
 
<p><strong>示例 2：</strong></p>
 
<pre>
<strong>输入：</strong>s = " &nbsp;hello world &nbsp;"
<strong>输出：</strong>"world hello"
<strong>解释：</strong>反转后的字符串中不能存在前导空格和尾随空格。
</pre>
 
<p><strong>示例 3：</strong></p>
 
<pre>
<strong>输入：</strong>s = "a good &nbsp; example"
<strong>输出：</strong>"example good a"
<strong>解释：</strong>如果两个单词间有多余的空格，反转后的字符串需要将单词间的空格减少到仅有一个。
</pre>
 
<p>&nbsp;</p>
 
<p><strong>提示：</strong></p>
 
<ul>
	<li><code>1 &lt;= s.length &lt;= 10<sup>4</sup></code></li>
	<li><code>s</code> 包含英文大小写字母、数字和空格 <code>' '</code></li>
	<li><code>s</code> 中 <strong>至少存在一个</strong> 单词</li>
</ul>
 
<ul>
</ul>
 
<p>&nbsp;</p>
 
<p><strong>进阶：</strong>如果字符串在你使用的编程语言中是一种可变数据类型，请尝试使用&nbsp;<code>O(1)</code> 额外空间复杂度的 <strong>原地</strong> 解法。</p>
 
 
 
---
 
[提交记录](https://leetcode.cn/problems/reverse-words-in-a-string/submissions/) | [题解](https://leetcode.cn/problems/reverse-words-in-a-string/solution/)

Solutions & Notes

properties:
  note.updated:
    displayName: Last Updated
  note.relative_links:
    displayName: Related Links
  note.desc:
    displayName: Description
  note.grade:
    displayName: Rating
  note.program_language:
    displayName: Language
  note.time_complexity:
    displayName: TC
  note.space_complexity:
    displayName: SC
views:
  - type: table
    name: Solutions & Notes
    filters:
      and:
        - file.hasLink(this.file)
        - file.tags.containsAny("leetcode/solution", "leetcode/note")
    order:
      - file.name
      - desc
      - program_language
      - time_complexity
      - space_complexity
      - grade
      - relative_links
      - updated
    sort:
      - property: grade
        direction: ASC
      - property: time_complexity
        direction: ASC
      - property: program_language
        direction: ASC
    columnSize:
      file.name: 104
      note.space_complexity: 65
      note.grade: 126

Similar Problems

properties:
  note.lcTopics:
    displayName: Topics
  note.lcAcRate:
    displayName: AC Rate
  note.favorites:
    displayName: Favorites
  note.grade:
    displayName: Rating
  note.translatedTitle:
    displayName: Title (CN)
  note.lcDifficulty:
    displayName: Difficulty
views:
  - type: table
    name: Similar Problems
    filters:
      and:
        - file.hasLink(this.file)
        - similarQuestions.contains(this.file)
    order:
      - file.name
      - translatedTitle
      - lcTopics
      - lcDifficulty
      - lcAcRate
      - grade
      - favorites
    sort:
      - property: file.name
        direction: ASC
      - property: lcTopics
        direction: DESC
    columnSize:
      note.translatedTitle: 240
      note.lcTopics: 347
      note.lcAcRate: 75
      note.grade: 122

Graph View

Backlinks