国外版

算法题（国外版）/find-the-town-judge.html

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+<p>In a town, there are <code>n</code> people labeled from <code>1</code> to <code>n</code>. There is a rumor that one of these people is secretly the town judge.</p>
+
+<p>If the town judge exists, then:</p>
+
+<ol>
+	<li>The town judge trusts nobody.</li>
+	<li>Everybody (except for the town judge) trusts the town judge.</li>
+	<li>There is exactly one person that satisfies properties <strong>1</strong> and <strong>2</strong>.</li>
+</ol>
+
+<p>You are given an array <code>trust</code> where <code>trust[i] = [a<sub>i</sub>, b<sub>i</sub>]</code> representing that the person labeled <code>a<sub>i</sub></code> trusts the person labeled <code>b<sub>i</sub></code>.</p>
+
+<p>Return <em>the label of the town judge if the town judge exists and can be identified, or return </em><code>-1</code><em> otherwise</em>.</p>
+
+<p>&nbsp;</p>
+<p><strong>Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> n = 2, trust = [[1,2]]
+<strong>Output:</strong> 2
+</pre>
+
+<p><strong>Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> n = 3, trust = [[1,3],[2,3]]
+<strong>Output:</strong> 3
+</pre>
+
+<p><strong>Example 3:</strong></p>
+
+<pre>
+<strong>Input:</strong> n = 3, trust = [[1,3],[2,3],[3,1]]
+<strong>Output:</strong> -1
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= n &lt;= 1000</code></li>
+	<li><code>0 &lt;= trust.length &lt;= 10<sup>4</sup></code></li>
+	<li><code>trust[i].length == 2</code></li>
+	<li>All the pairs of <code>trust</code> are <strong>unique</strong>.</li>
+	<li><code>a<sub>i</sub> != b<sub>i</sub></code></li>
+	<li><code>1 &lt;= a<sub>i</sub>, b<sub>i</sub> &lt;= n</code></li>
+</ul>