Sync LeetCode submission Runtime - 0 ms (100.00%), Memory - 18 MB (100.00%)

Author: jimit105

3736-find-valid-pair-of-adjacent-digits-in-string/README.md

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+<p>You are given a string <code>s</code> consisting only of digits. A <strong>valid pair</strong> is defined as two <strong>adjacent</strong> digits in <code>s</code> such that:</p>
+
+<ul>
+	<li>The first digit is <strong>not equal</strong> to the second.</li>
+	<li>Each digit in the pair appears in <code>s</code> <strong>exactly</strong> as many times as its numeric value.</li>
+</ul>
+
+<p>Return the first <strong>valid pair</strong> found in the string <code>s</code> when traversing from left to right. If no valid pair exists, return an empty string.</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;2523533&quot;</span></p>
+
+<p><strong>Output:</strong> <span class="example-io">&quot;23&quot;</span></p>
+
+<p><strong>Explanation:</strong></p>
+
+<p>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>.</p>
+</div>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<div class="example-block">
+<p><strong>Input:</strong> <span class="example-io">s = &quot;221&quot;</span></p>
+
+<p><strong>Output:</strong> <span class="example-io">&quot;21&quot;</span></p>
+
+<p><strong>Explanation:</strong></p>
+
+<p>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>.</p>
+</div>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<div class="example-block">
+<p><strong>Input:</strong> <span class="example-io">s = &quot;22&quot;</span></p>
+
+<p><strong>Output:</strong> <span class="example-io">&quot;&quot;</span></p>
+
+<p><strong>Explanation:</strong></p>
+
+<p>There are no valid adjacent pairs.</p>
+</div>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<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>

3736-find-valid-pair-of-adjacent-digits-in-string/solution.py

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+# Time: O(n)
+# Space: O(1)
+
+from collections import Counter
+
+class Solution:
+    def findValidPair(self, s: str) -> str:
+        freq = Counter(s)
+
+        for i in range(len(s) - 1):
+            first = s[i]
+            second = s[i + 1]
+
+            if (first != second and
+                freq[first] == int(first) and
+                freq[second] == int(second)):
+
+                return first + second
+
+        return ''
+