Integer Replacement
<p>Given a positive integer <code>n</code>,&nbsp;you can apply one of the following&nbsp;operations:</p>

<ol>
	<li>If <code>n</code> is even, replace <code>n</code> with <code>n / 2</code>.</li>
	<li>If <code>n</code> is odd, replace <code>n</code> with either <code>n + 1</code> or <code>n - 1</code>.</li>
</ol>

<p>Return <em>the minimum number of operations needed for</em> <code>n</code> <em>to become</em> <code>1</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> n = 8
<strong>Output:</strong> 3
<strong>Explanation:</strong> 8 -&gt; 4 -&gt; 2 -&gt; 1
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> n = 7
<strong>Output:</strong> 4
<strong>Explanation: </strong>7 -&gt; 8 -&gt; 4 -&gt; 2 -&gt; 1
or 7 -&gt; 6 -&gt; 3 -&gt; 2 -&gt; 1
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> n = 4
<strong>Output:</strong> 2
</pre>

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

<ul>
	<li><code>1 &lt;= n &lt;= 2<sup>31</sup> - 1</code></li>
</ul>
Greedy; Bit Manipulation; Memoization; Dynamic Programming
func integerReplacement(n int) int {
	ans := 0
	for n != 1 {
		if (n & 1) == 0 {
			n >>= 1
		} else if n != 3 && (n&3) == 3 {
			n++
		} else {
			n--
		}
		ans++
	}
	return ans
}