find-special-substring-of-length-k

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Algorithms

You are given a string <code>s</code> and an integer <code>k</code>.

Determine if there exists a substring of length exactly <code>k</code> in <code>s</code> that satisfies the following conditions:

<ol>
	<li>The substring consists of only one distinct character (e.g., <code>&quot;aaa&quot;</code> or <code>&quot;bbb&quot;</code>).</li>
	<li>If there is a character immediately before the substring, it must be different from the character in the substring.</li>
	<li>If there is a character immediately after the substring, it must also be different from the character in the substring.</li>
</ol>

Return <code>true</code> if such a substring exists. Otherwise, return <code>false</code>.

&nbsp;
Example 1:

<div class="example-block">
Input: s = &quot;aaabaaa&quot;, k = 3

Output: true

Explanation:

The substring <code>s[4..6] == &quot;aaa&quot;</code> satisfies the conditions.

<ul>
	<li>It has a length of 3.</li>
	<li>All characters are the same.</li>
	<li>The character before <code>&quot;aaa&quot;</code> is <code>&#39;b&#39;</code>, which is different from <code>&#39;a&#39;</code>.</li>
	<li>There is no character after <code>&quot;aaa&quot;</code>.</li>
</ul>
</div>

Example 2:

<div class="example-block">
Input: s = &quot;abc&quot;, k = 2

Output: false

Explanation:

There is no substring of length 2 that consists of one distinct character and satisfies the conditions.
</div>

&nbsp;
Constraints:

<ul>
	<li><code>1 &lt;= k &lt;= s.length &lt;= 100</code></li>
	<li><code>s</code> consists of lowercase English letters only.</li>
</ul>

hasSpecialSubstring

Find Special Substring of Length K

String

给你一个字符串 <code>s</code> 和一个整数 <code>k</code>。

判断是否存在一个长度&nbsp;恰好&nbsp;为 <code>k</code> 的子字符串，该子字符串需要满足以下条件：

<ol>
	<li>该子字符串&nbsp;只包含一个唯一字符（例如，<code>"aaa"</code> 或 <code>"bbb"</code>）。</li>
	<li>如果该子字符串的&nbsp;前面&nbsp;有字符，则该字符必须与子字符串中的字符不同。</li>
	<li>如果该子字符串的&nbsp;后面&nbsp;有字符，则该字符也必须与子字符串中的字符不同。</li>
</ol>

如果存在这样的子串，返回 <code>true</code>；否则，返回 <code>false</code>。

子字符串&nbsp;是字符串中的连续、非空字符序列。

&nbsp;

示例 1：

<div class="example-block">
输入： s = "aaabaaa", k = 3

输出： true

解释：

子字符串 <code>s[4..6] == "aaa"</code> 满足条件：

<ul>
	<li>长度为 3。</li>
	<li>所有字符相同。</li>
	<li>子串 <code>"aaa"</code> 前的字符是 <code>'b'</code>，与 <code>'a'</code> 不同。</li>
	<li>子串 <code>"aaa"</code> 后没有字符。</li>
</ul>
</div>

示例 2：

<div class="example-block">
输入： s = "abc", k = 2

输出： false

解释：

不存在长度为 2 、仅由一个唯一字符组成且满足所有条件的子字符串。
</div>

&nbsp;

提示：

<ul>
	<li><code>1 &lt;= k &lt;= s.length &lt;= 100</code></li>
	<li><code>s</code> 仅由小写英文字母组成。</li>
</ul>