国外版

算法题（国外版）/unique-number-of-occurrences.html

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+<p>Given an array of integers <code>arr</code>, return <code>true</code> if the number of occurrences of each value in the array is <strong>unique</strong>, or <code>false</code> otherwise.</p>
+
+<p>&nbsp;</p>
+<p><strong>Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> arr = [1,2,2,1,1,3]
+<strong>Output:</strong> true
+<strong>Explanation:</strong>&nbsp;The value 1 has 3 occurrences, 2 has 2 and 3 has 1. No two values have the same number of occurrences.</pre>
+
+<p><strong>Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> arr = [1,2]
+<strong>Output:</strong> false
+</pre>
+
+<p><strong>Example 3:</strong></p>
+
+<pre>
+<strong>Input:</strong> arr = [-3,0,1,-3,1,1,1,-3,10,0]
+<strong>Output:</strong> true
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= arr.length&nbsp;&lt;= 1000</code></li>
+	<li><code>-1000 &lt;= arr[i] &lt;= 1000</code></li>
+</ul>