<p>Write a program to swap odd and even bits in an integer with as few instructions as possible (e.g., bit 0 and bit 1 are swapped, bit 2 and bit 3 are swapped, and so on).</p>
<p><strong>Example1:</strong></p>
<pre>
<strong> Input</strong>: num = 2（0b10）
<strong> Output</strong> 1 (0b01)
</pre>
<p><strong>Example2:</strong></p>
<pre>
<strong> Input</strong>: num = 3
<strong> Output</strong>: 3
</pre>
<p><strong>Note:</strong></p>
<ol>
<li><code>0 <= num <=</code> 2^30 - 1</li>
<li>The result integer fits into 32-bit integer.</li>
