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Author: jimit105

1510-find-lucky-integer-in-an-array/README.md

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+<p>Given an array of integers <code>arr</code>, a <strong>lucky integer</strong> is an integer that has a frequency in the array equal to its value.</p>
+
+<p>Return <em>the largest <strong>lucky integer</strong> in the array</em>. If there is no <strong>lucky integer</strong> return <code>-1</code>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> arr = [2,2,3,4]
+<strong>Output:</strong> 2
+<strong>Explanation:</strong> The only lucky number in the array is 2 because frequency[2] == 2.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> arr = [1,2,2,3,3,3]
+<strong>Output:</strong> 3
+<strong>Explanation:</strong> 1, 2 and 3 are all lucky numbers, return the largest of them.
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<pre>
+<strong>Input:</strong> arr = [2,2,2,3,3]
+<strong>Output:</strong> -1
+<strong>Explanation:</strong> There are no lucky numbers in the array.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= arr.length &lt;= 500</code></li>
+	<li><code>1 &lt;= arr[i] &lt;= 500</code></li>
+</ul>

1510-find-lucky-integer-in-an-array/solution.py

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+# Approach 3: Counter
+
+# Time: O(n)
+# Space: O(n)
+
+from collections import Counter
+
+class Solution:
+    def findLucky(self, arr: List[int]) -> int:
+        counts = Counter(arr)
+        lucky_num = -1
+
+        for num, count in counts.items():
+            if num == count:
+                lucky_num = max(lucky_num, num)
+
+        return lucky_num
+