leetcode-problemset/leetcode-cn/problem (English)/检查整数及其两倍数是否存在(English) [check-if-n-and-its-double-exist].html

<p>Given an array <code>arr</code> of integers, check if there exists two integers <code>N</code> and <code>M</code> such that <code>N</code> is the double of <code>M</code> ( i.e. <code>N = 2 * M</code>).</p>

<p>More formally check if there exists&nbsp;two indices <code>i</code> and <code>j</code> such that :</p>

<ul>
	<li><code>i != j</code></li>
	<li><code>0 &lt;= i, j &lt; arr.length</code></li>
	<li><code>arr[i] == 2 * arr[j]</code></li>
</ul>

<p>&nbsp;</p>
<p><strong>Example 1:</strong></p>

<pre>
<strong>Input:</strong> arr = [10,2,5,3]
<strong>Output:</strong> true
<strong>Explanation:</strong> N<code> = 10</code> is the double of M<code> = 5</code>,that is, <code>10 = 2 * 5</code>.
</pre>

<p><strong>Example 2:</strong></p>

<pre>
<strong>Input:</strong> arr = [7,1,14,11]
<strong>Output:</strong> true
<strong>Explanation:</strong> N<code> = 14</code> is the double of M<code> = 7</code>,that is, <code>14 = 2 * 7</code>.
</pre>

<p><strong>Example 3:</strong></p>

<pre>
<strong>Input:</strong> arr = [3,1,7,11]
<strong>Output:</strong> false
<strong>Explanation:</strong> In this case does not exist N and M, such that N = 2 * M.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>2 &lt;= arr.length &lt;= 500</code></li>
	<li><code>-10^3 &lt;= arr[i] &lt;= 10^3</code></li>
</ul>