Project Notes

Valid Number

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Description

tab: English
 
<p>Given a string <code>s</code>, return whether <code>s</code> is a <strong>valid number</strong>.<br />
<br />
For example, all the following are valid numbers: <code>&quot;2&quot;, &quot;0089&quot;, &quot;-0.1&quot;, &quot;+3.14&quot;, &quot;4.&quot;, &quot;-.9&quot;, &quot;2e10&quot;, &quot;-90E3&quot;, &quot;3e+7&quot;, &quot;+6e-1&quot;, &quot;53.5e93&quot;, &quot;-123.456e789&quot;</code>, while the following are not valid numbers: <code>&quot;abc&quot;, &quot;1a&quot;, &quot;1e&quot;, &quot;e3&quot;, &quot;99e2.5&quot;, &quot;--6&quot;, &quot;-+3&quot;, &quot;95a54e53&quot;</code>.</p>
 
<p>Formally, a&nbsp;<strong>valid number</strong> is defined using one of the following definitions:</p>
 
<ol>
	<li>An <strong>integer number</strong> followed by an <strong>optional exponent</strong>.</li>
	<li>A <strong>decimal number</strong> followed by an <strong>optional exponent</strong>.</li>
</ol>
 
<p>An <strong>integer number</strong> is defined with an <strong>optional sign</strong> <code>&#39;-&#39;</code> or <code>&#39;+&#39;</code> followed by <strong>digits</strong>.</p>
 
<p>A <strong>decimal number</strong> is defined with an <strong>optional sign</strong> <code>&#39;-&#39;</code> or <code>&#39;+&#39;</code> followed by one of the following definitions:</p>
 
<ol>
	<li><strong>Digits</strong> followed by a <strong>dot</strong> <code>&#39;.&#39;</code>.</li>
	<li><strong>Digits</strong> followed by a <strong>dot</strong> <code>&#39;.&#39;</code> followed by <strong>digits</strong>.</li>
	<li>A <strong>dot</strong> <code>&#39;.&#39;</code> followed by <strong>digits</strong>.</li>
</ol>
 
<p>An <strong>exponent</strong> is defined with an <strong>exponent notation</strong> <code>&#39;e&#39;</code> or <code>&#39;E&#39;</code> followed by an <strong>integer number</strong>.</p>
 
<p>The <strong>digits</strong> are defined as one or more digits.</p>
 
<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
 
<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">s = &quot;0&quot;</span></p>
 
<p><strong>Output:</strong> <span class="example-io">true</span></p>
</div>
 
<p><strong class="example">Example 2:</strong></p>
 
<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">s = &quot;e&quot;</span></p>
 
<p><strong>Output:</strong> <span class="example-io">false</span></p>
</div>
 
<p><strong class="example">Example 3:</strong></p>
 
<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">s = &quot;.&quot;</span></p>
 
<p><strong>Output:</strong> <span class="example-io">false</span></p>
</div>
 
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>
 
<ul>
	<li><code>1 &lt;= s.length &lt;= 20</code></li>
	<li><code>s</code> consists of only English letters (both uppercase and lowercase), digits (<code>0-9</code>), plus <code>&#39;+&#39;</code>, minus <code>&#39;-&#39;</code>, or dot <code>&#39;.&#39;</code>.</li>
</ul>
 
 
 
---
 
[submissions](https://leetcode.com/problems/valid-number/submissions/) | [solutions](https://leetcode.com/problems/valid-number/solutions/)
 
 
tab: 中文
 
<p>给定一个字符串&nbsp;<code>s</code>&nbsp;，返回&nbsp;<code>s</code>&nbsp;是否是一个 <strong>有效数字</strong>。</p>
 
<p>例如，下面的都是有效数字：<code>"2", "0089", "-0.1", "+3.14", "4.", "-.9", "2e10", "-90E3", "3e+7", "+6e-1", "53.5e93", "-123.456e789"</code>，而接下来的不是：<code>"abc", "1a", "1e", "e3", "99e2.5", "--6", "-+3", "95a54e53"</code>。</p>
 
<p>一般的，一个 <strong>有效数字</strong>&nbsp;可以用以下的规则之一定义：</p>
 
<ol>
	<li>一个 <strong>整数</strong> 后面跟着一个 <strong>可选指数</strong>。</li>
	<li>一个 <strong>十进制数</strong> 后面跟着一个&nbsp;<strong>可选指数</strong>。</li>
</ol>
 
<p>一个 <strong>整数</strong> 定义为一个&nbsp;<strong>可选符号</strong>&nbsp;<code>'-'</code>&nbsp;或&nbsp;<code>'+'</code>&nbsp;后面跟着 <strong>数字</strong>。</p>
 
<p>一个 <strong>十进制数</strong>&nbsp;定义为一个&nbsp;<strong>可选符号&nbsp;</strong><code>'-'</code>&nbsp;或&nbsp;<code>'+'</code>&nbsp;后面跟着下述规则：</p>
 
<ol>
	<li><strong>数字&nbsp;</strong>后跟着一个 <strong>小数点&nbsp;<code>.</code></strong>。</li>
	<li><strong>数字&nbsp;</strong>后跟着一个 <strong>小数点&nbsp;<code>.</code>&nbsp;</strong>再跟着<strong> 数位</strong>。</li>
	<li>一个 <strong>小数点&nbsp;<code>.</code>&nbsp;</strong>后跟着<strong> 数位</strong>。</li>
</ol>
 
<p><strong>指数</strong> 定义为指数符号 <code>'e'</code> 或 <code>'E'</code>，后面跟着一个 <b>整数</b>。</p>
 
<p><strong>数字</strong>&nbsp;定义为一个或多个数位。</p>
 
<p>&nbsp;</p>
 
<p><strong class="example">示例 1：</strong></p>
 
<div class="example-block">
<p><strong>输入：</strong><span class="example-io">s = "0"</span></p>
 
<p><strong>输出：</strong><span class="example-io">true</span></p>
</div>
 
<p><strong class="example">示例 2：</strong></p>
 
<div class="example-block">
<p><strong>输入：</strong><span class="example-io">s = "e"</span></p>
 
<p><strong>输出：</strong><span class="example-io">false</span></p>
</div>
 
<p><strong class="example">示例 3：</strong></p>
 
<div class="example-block">
<p><strong>输入：</strong><span class="example-io">s = "."</span></p>
 
<p><strong>输出：</strong><span class="example-io">false</span></p>
</div>
 
<p>&nbsp;</p>
 
<p><strong>提示：</strong></p>
 
<ul>
	<li><code>1 &lt;= s.length &lt;= 20</code></li>
	<li><code>s</code> 仅含英文字母（大写和小写），数字（<code>0-9</code>），加号 <code>'+'</code> ，减号 <code>'-'</code> ，或者点 <code>'.'</code> 。</li>
</ul>
 
 
 
---
 
[提交记录](https://leetcode.cn/problems/valid-number/submissions/) | [题解](https://leetcode.cn/problems/valid-number/solution/)

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