<div><p>Reverse bits of a given 32 bits unsigned integer.</p>
<p><strong>Note:</strong></p>
<ul>
<li>Note that in some languages such as Java, there is no unsigned integer type. In this case, both input and output will be given as a signed integer type. They should not affect your implementation, as the integer's internal binary representation is the same, whether it is signed or unsigned.</li>
<li>In Java, the compiler represents the signed integers using <a href="https://en.wikipedia.org/wiki/Two%27s_complement" target="_blank">2's complement notation</a>. Therefore, in <strong>Example 2</strong> above, the input represents the signed integer <code>-3</code> and the output represents the signed integer <code>-1073741825</code>.</li>
</ul>
<p><b>Follow up</b>:</p>
<p>If this function is called many times, how would you optimize it?</p>
<p> </p>
<p><strong>Example 1:</strong></p>
<pre><strong>Input:</strong> n = 00000010100101000001111010011100
<strong>Output:</strong> 964176192 (00111001011110000010100101000000)
<strong>Explanation: </strong>The input binary string <strong>00000010100101000001111010011100</strong> represents the unsigned integer 43261596, so return 964176192 which its binary representation is <strong>00111001011110000010100101000000</strong>.
</pre>
<p><strong>Example 2:</strong></p>
<pre><strong>Input:</strong> n = 11111111111111111111111111111101
<strong>Output:</strong> 3221225471 (10111111111111111111111111111111)
<strong>Explanation: </strong>The input binary string <strong>11111111111111111111111111111101</strong> represents the unsigned integer 4294967293, so return 3221225471 which its binary representation is <strong>10111111111111111111111111111111</strong>.
</pre>
<p> </p>
<p><strong>Constraints:</strong></p>
<ul>
<li>The input must be a <strong>binary string</strong> of length <code>32</code></li>
</ul>
</div>