number-of-valid-words-in-a-sentence

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Algorithms

A sentence consists of lowercase letters (<code>&#39;a&#39;</code> to <code>&#39;z&#39;</code>), digits (<code>&#39;0&#39;</code> to <code>&#39;9&#39;</code>), hyphens (<code>&#39;-&#39;</code>), punctuation marks (<code>&#39;!&#39;</code>, <code>&#39;.&#39;</code>, and <code>&#39;,&#39;</code>), and spaces (<code>&#39; &#39;</code>) only. Each sentence can be broken down into one or more tokens separated by one or more spaces <code>&#39; &#39;</code>.

A token is a valid word if all three of the following are true:

<ul>
	<li>It only contains lowercase letters, hyphens, and/or punctuation (no digits).</li>
	<li>There is at most one hyphen <code>&#39;-&#39;</code>. If present, it must be surrounded by lowercase characters (<code>&quot;a-b&quot;</code> is valid, but <code>&quot;-ab&quot;</code> and <code>&quot;ab-&quot;</code> are not valid).</li>
	<li>There is at most one punctuation mark. If present, it must be at the end of the token (<code>&quot;ab,&quot;</code>, <code>&quot;cd!&quot;</code>, and <code>&quot;.&quot;</code> are valid, but <code>&quot;a!b&quot;</code> and <code>&quot;c.,&quot;</code> are not valid).</li>
</ul>

Examples of valid words include <code>&quot;a-b.&quot;</code>, <code>&quot;afad&quot;</code>, <code>&quot;ba-c&quot;</code>, <code>&quot;a!&quot;</code>, and <code>&quot;!&quot;</code>.

Given a string <code>sentence</code>, return the number of valid words in <code>sentence</code>.

&nbsp;
Example 1:

<pre>
Input: sentence = &quot;cat and dog&quot;
Output: 3
Explanation: The valid words in the sentence are &quot;cat&quot;, &quot;and&quot;, and &quot;dog&quot;.
</pre>

Example 2:

<pre>
Input: sentence = &quot;!this 1-s b8d!&quot;
Output: 0
Explanation: There are no valid words in the sentence.
&quot;!this&quot; is invalid because it starts with a punctuation mark.
&quot;1-s&quot; and &quot;b8d&quot; are invalid because they contain digits.
</pre>

Example 3:

<pre>
Input: sentence = &quot;alice and bob are playing stone-game10&quot;
Output: 5
Explanation: The valid words in the sentence are &quot;alice&quot;, &quot;and&quot;, &quot;bob&quot;, &quot;are&quot;, and &quot;playing&quot;.
&quot;stone-game10&quot; is invalid because it contains digits.
</pre>

&nbsp;
Constraints:

<ul>
	<li><code>1 &lt;= sentence.length &lt;= 1000</code></li>
	<li><code>sentence</code> only contains lowercase English letters, digits, <code>&#39; &#39;</code>, <code>&#39;-&#39;</code>, <code>&#39;!&#39;</code>, <code>&#39;.&#39;</code>, and <code>&#39;,&#39;</code>.</li>
	<li>There will be at least&nbsp;<code>1</code> token.</li>
</ul>

countValidWords

Number of Valid Words in a Sentence

Maximum Number of Words Found in Sentences

maximum-number-of-words-found-in-sentences

句子中的最多单词数

String

句子仅由小写字母（<code>'a'</code> 到 <code>'z'</code>）、数字（<code>'0'</code> 到 <code>'9'</code>）、连字符（<code>'-'</code>）、标点符号（<code>'!'</code>、<code>'.'</code> 和 <code>','</code>）以及空格（<code>' '</code>）组成。每个句子可以根据空格分解成 一个或者多个 token ，这些 token 之间由一个或者多个空格 <code>' '</code> 分隔。

如果一个 token 同时满足下述条件，则认为这个 token 是一个有效单词：

<ul>
	<li>仅由小写字母、连字符和/或标点（不含数字）组成。</li>
	<li>至多一个 连字符 <code>'-'</code> 。如果存在，连字符两侧应当都存在小写字母（<code>"a-b"</code> 是一个有效单词，但 <code>"-ab"</code> 和 <code>"ab-"</code> 不是有效单词）。</li>
	<li>至多一个 标点符号。如果存在，标点符号应当位于 token 的 末尾 。</li>
</ul>

这里给出几个有效单词的例子：<code>"a-b."</code>、<code>"afad"</code>、<code>"ba-c"</code>、<code>"a!"</code> 和 <code>"!"</code> 。

给你一个字符串 <code>sentence</code> ，请你找出并返回 <code>sentence</code> 中 有效单词的数目 。

&nbsp;

示例 1：

<pre>
输入：sentence = "cat and dog"
输出：3
解释：句子中的有效单词是 "cat"、"and" 和 "dog"
</pre>

示例 2：

<pre>
输入：sentence = "!this 1-s b8d!"
输出：0
解释：句子中没有有效单词
"!this" 不是有效单词，因为它以一个标点开头
"1-s" 和 "b8d" 也不是有效单词，因为它们都包含数字
</pre>

示例 3：

<pre>
输入：sentence = "alice and bob are playing stone-game10"
输出：5
解释：句子中的有效单词是 "alice"、"and"、"bob"、"are" 和 "playing"
"stone-game10" 不是有效单词，因为它含有数字
</pre>

&nbsp;

提示：

<ul>
	<li><code>1 &lt;= sentence.length &lt;= 1000</code></li>
	<li><code>sentence</code> 由小写英文字母、数字（<code>0-9</code>）、以及字符（<code>' '</code>、<code>'-'</code>、<code>'!'</code>、<code>'.'</code> 和 <code>','</code>）组成</li>
	<li>句子中至少有 <code>1</code> 个 token</li>
</ul>