Sync LeetCode submission Runtime - 45 ms (88.17%), Memory - 49.3 MB (6.17%)

Author: DhanushNehru

2427-first-letter-to-appear-twice/README.md

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+<p>Given a string <code>s</code> consisting of lowercase English letters, return <em>the first letter to appear <strong>twice</strong></em>.</p>
+
+<p><strong>Note</strong>:</p>
+
+<ul>
+	<li>A letter <code>a</code> appears twice before another letter <code>b</code> if the <strong>second</strong> occurrence of <code>a</code> is before the <strong>second</strong> occurrence of <code>b</code>.</li>
+	<li><code>s</code> will contain at least one letter that appears twice.</li>
+</ul>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> s = &quot;abccbaacz&quot;
+<strong>Output:</strong> &quot;c&quot;
+<strong>Explanation:</strong>
+The letter &#39;a&#39; appears on the indexes 0, 5 and 6.
+The letter &#39;b&#39; appears on the indexes 1 and 4.
+The letter &#39;c&#39; appears on the indexes 2, 3 and 7.
+The letter &#39;z&#39; appears on the index 8.
+The letter &#39;c&#39; is the first letter to appear twice, because out of all the letters the index of its second occurrence is the smallest.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> s = &quot;abcdd&quot;
+<strong>Output:</strong> &quot;d&quot;
+<strong>Explanation:</strong>
+The only letter that appears twice is &#39;d&#39; so we return &#39;d&#39;.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>2 &lt;= s.length &lt;= 100</code></li>
+	<li><code>s</code> consists of lowercase English letters.</li>
+	<li><code>s</code> has at least one repeated letter.</li>
+</ul>

2427-first-letter-to-appear-twice/solution.js

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+/**
+ * @param {string} s
+ * @return {character}
+ */
+var repeatedCharacter = function(s) {
+    let hash = {}
+
+    for(let i=0;i<s.length;i++){
+        hash[s[i]] = hash[s[i]] ? hash[s[i]] + 1 : 1
+
+        if(hash[s[i]] == 2){
+            return s[i]
+        }
+    }
+};