add leetcode problem-cn part1

算法题（国内版）/problem (Chinese)/有效的回旋镖 [valid-boomerang].html

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+<p>给定一个数组<meta charset="UTF-8" />&nbsp;<code>points</code>&nbsp;，其中<meta charset="UTF-8" />&nbsp;<code>points[i] = [x<sub>i</sub>, y<sub>i</sub>]</code>&nbsp;表示 <strong>X-Y</strong> 平面上的一个点，<em>如果这些点构成一个&nbsp;</em><strong>回旋镖</strong>&nbsp;则返回&nbsp;<code>true</code>&nbsp;。</p>
+
+<p><strong>回旋镖</strong>&nbsp;定义为一组三个点，这些点&nbsp;<strong>各不相同</strong>&nbsp;且&nbsp;<strong>不在一条直线上</strong>&nbsp;。</p>
+
+<p>&nbsp;</p>
+
+<p><strong>示例 1：</strong></p>
+
+<pre>
+<strong>输入：</strong>points = [[1,1],[2,3],[3,2]]
+<strong>输出：</strong>true
+</pre>
+
+<p><strong>示例 2：</strong></p>
+
+<pre>
+<strong>输入：</strong>points = [[1,1],[2,2],[3,3]]
+<strong>输出：</strong>false</pre>
+
+<p>&nbsp;</p>
+
+<p><strong>提示：</strong></p>
+<meta charset="UTF-8" />
+
+<ul>
+	<li><code>points.length == 3</code></li>
+	<li><code>points[i].length == 2</code></li>
+	<li><code>0 &lt;= x<sub>i</sub>, y<sub>i</sub>&nbsp;&lt;= 100</code></li>
+</ul>