Minimum Operations to Make Array Equal
<p>You have an array <code>arr</code> of length <code>n</code> where <code>arr[i] = (2 * i) + 1</code> for all valid values of <code>i</code> (i.e.,&nbsp;<code>0 &lt;= i &lt; n</code>).</p>

<p>In one operation, you can select two indices <code>x</code> and <code>y</code> where <code>0 &lt;= x, y &lt; n</code> and subtract <code>1</code> from <code>arr[x]</code> and add <code>1</code> to <code>arr[y]</code> (i.e., perform <code>arr[x] -=1 </code>and <code>arr[y] += 1</code>). The goal is to make all the elements of the array <strong>equal</strong>. It is <strong>guaranteed</strong> that all the elements of the array can be made equal using some operations.</p>

<p>Given an integer <code>n</code>, the length of the array, return <em>the minimum number of operations</em> needed to make all the elements of arr equal.</p>

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

<pre>
<strong>Input:</strong> n = 3
<strong>Output:</strong> 2
<strong>Explanation:</strong> arr = [1, 3, 5]
First operation choose x = 2 and y = 0, this leads arr to be [2, 3, 4]
In the second operation choose x = 2 and y = 0 again, thus arr = [3, 3, 3].
</pre>

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

<pre>
<strong>Input:</strong> n = 6
<strong>Output:</strong> 9
</pre>

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

<ul>
	<li><code>1 &lt;= n &lt;= 10<sup>4</sup></code></li>
</ul>
Math
func minOperations(n int) (ans int) {
	for i := 0; i < n>>1; i++ {
		ans += n - (i<<1 | 1)
	}
	return
}