find-valid-pair-of-adjacent-digits-in-string

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Algorithms

You are given a string <code>s</code> consisting only of digits. A valid pair is defined as two adjacent digits in <code>s</code> such that:

<ul>
	<li>The first digit is not equal to the second.</li>
	<li>Each digit in the pair appears in <code>s</code> exactly as many times as its numeric value.</li>
</ul>

Return the first valid pair found in the string <code>s</code> when traversing from left to right. If no valid pair exists, return an empty string.

&nbsp;
Example 1:

<div class="example-block">
Input: s = &quot;2523533&quot;

Output: &quot;23&quot;

Explanation:

Digit <code>&#39;2&#39;</code> appears 2 times and digit <code>&#39;3&#39;</code> appears 3 times. Each digit in the pair <code>&quot;23&quot;</code> appears in <code>s</code> exactly as many times as its numeric value. Hence, the output is <code>&quot;23&quot;</code>.
</div>

Example 2:

<div class="example-block">
Input: s = &quot;221&quot;

Output: &quot;21&quot;

Explanation:

Digit <code>&#39;2&#39;</code> appears 2 times and digit <code>&#39;1&#39;</code> appears 1 time. Hence, the output is <code>&quot;21&quot;</code>.
</div>

Example 3:

<div class="example-block">
Input: s = &quot;22&quot;

Output: &quot;&quot;

Explanation:

There are no valid adjacent pairs.
</div>

&nbsp;
Constraints:

<ul>
	<li><code>2 &lt;= s.length &lt;= 100</code></li>
	<li><code>s</code> only consists of digits from <code>&#39;1&#39;</code> to <code>&#39;9&#39;</code>.</li>
</ul>

findValidPair

Find Valid Pair of Adjacent Digits in String

Majority Element

majority-element

多数元素

Contains Duplicate

contains-duplicate

存在重复元素

Hash Table

String

Counting

给你一个只包含数字的字符串&nbsp;<code>s</code>&nbsp;。如果 <code>s</code>&nbsp;中两个 相邻&nbsp;的数字满足以下条件，我们称它们是 合法的&nbsp;：

<ul>
	<li>前面的数字 不等于 第二个数字。</li>
	<li>两个数字在 <code>s</code>&nbsp;中出现的次数 恰好&nbsp;分别等于这个数字本身。</li>
</ul>

请你从左到右遍历字符串 <code>s</code>&nbsp;，并返回最先找到的 合法&nbsp;相邻数字。如果这样的相邻数字不存在，请你返回一个空字符串。

&nbsp;

示例 1：

<div class="example-block">
输入：s = "2523533"

输出："23"

解释：

数字&nbsp;<code>'2'</code>&nbsp;出现 2 次，数字&nbsp;<code>'3'</code>&nbsp;出现 3 次。<code>"23"</code>&nbsp;中每个数字在 <code>s</code>&nbsp;中出现的次数都恰好分别等于数字本身。所以输出&nbsp;<code>"23"</code>&nbsp;。
</div>

示例 2：

<div class="example-block">
输入：s = "221"

输出："21"

解释：

数字&nbsp;<code>'2'</code>&nbsp;出现 2 次，数字&nbsp;<code>'1'</code>&nbsp;出现 1 次。所以输出&nbsp;<code>"21"</code>&nbsp;。
</div>

示例 3：

<div class="example-block">
输入：s = "22"

输出：""

解释：

没有合法的相邻数字。
</div>

&nbsp;

提示：

<ul>
	<li><code>2 &lt;= s.length &lt;= 100</code></li>
	<li><code>s</code>&nbsp;只包含&nbsp;<code>'1'</code> 到&nbsp;<code>'9'</code> 的数字。</li>
</ul>