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leetcode-problemset/leetcode-cn/problem (English)/统计可以被最后一个数位整除的子字符串数目(English) [count-substrings-divisible-by-last-digit].html
2025-02-22 16:46:22 +08:00

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<p>You are given a string <code>s</code> consisting of digits.</p>
<p>Return the <strong>number</strong> of <span data-keyword="substring-nonempty">substrings</span> of <code>s</code> <strong>divisible</strong> by their <strong>non-zero</strong> last digit.</p>
<p><strong>Note</strong>: A substring may contain leading zeros.</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;12936&quot;</span></p>
<p><strong>Output:</strong> <span class="example-io">11</span></p>
<p><strong>Explanation:</strong></p>
<p>Substrings <code>&quot;29&quot;</code>, <code>&quot;129&quot;</code>, <code>&quot;293&quot;</code> and <code>&quot;2936&quot;</code> are not divisible by their last digit. There are 15 substrings in total, so the answer is <code>15 - 4 = 11</code>.</p>
</div>
<p><strong class="example">Example 2:</strong></p>
<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">s = &quot;5701283&quot;</span></p>
<p><strong>Output:</strong> <span class="example-io">18</span></p>
<p><strong>Explanation:</strong></p>
<p>Substrings <code>&quot;01&quot;</code>, <code>&quot;12&quot;</code>, <code>&quot;701&quot;</code>, <code>&quot;012&quot;</code>, <code>&quot;128&quot;</code>, <code>&quot;5701&quot;</code>, <code>&quot;7012&quot;</code>, <code>&quot;0128&quot;</code>, <code>&quot;57012&quot;</code>, <code>&quot;70128&quot;</code>, <code>&quot;570128&quot;</code>, and <code>&quot;701283&quot;</code> are all divisible by their last digit. Additionally, all substrings that are just 1 non-zero digit are divisible by themselves. Since there are 6 such digits, the answer is <code>12 + 6 = 18</code>.</p>
</div>
<p><strong class="example">Example 3:</strong></p>
<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">s = &quot;1010101010&quot;</span></p>
<p><strong>Output:</strong> <span class="example-io">25</span></p>
<p><strong>Explanation:</strong></p>
<p>Only substrings that end with digit <code>&#39;1&#39;</code> are divisible by their last digit. There are 25 such substrings.</p>
</div>
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>
<ul>
<li><code>1 &lt;= s.length &lt;= 10<sup>5</sup></code></li>
<li><code>s</code> consists of digits only.</li>
</ul>