<p>You are given an integer array <code>nums</code>. The <em>value</em> of this array is defined as the sum of <code>|nums[i] - nums[i + 1]|</code> for all <code>0 &lt;= i &lt; nums.length - 1</code>.</p>

<p>You are allowed to select any subarray of the given array and reverse it. You can perform this operation <strong>only once</strong>.</p>

<p>Find maximum possible value of the final array.</p>

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

<pre>
<strong>Input:</strong> nums = [2,3,1,5,4]
<strong>Output:</strong> 10
<b>Explanation: </b>By reversing the subarray [3,1,5] the array becomes [2,5,1,3,4] whose value is 10.
</pre>

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

<pre>
<strong>Input:</strong> nums = [2,4,9,24,2,1,10]
<strong>Output:</strong> 68
</pre>

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

<ul>
	<li><code>2 &lt;= nums.length &lt;= 3 * 10<sup>4</sup></code></li>
	<li><code>-10<sup>5</sup> &lt;= nums[i] &lt;= 10<sup>5</sup></code></li>
	<li>The answer is guaranteed to fit in a 32-bit integer.</li>
</ul>

from itertools import tee
class Solution:
    def maxValueAfterReverse(self, nums):
        it1, it2 = tee(nums, 2)
        next(it2)
        inc = total = 0
        first, last, mx, mn = nums[0], nums[-1], -100000, 100000
        for f, b in zip(it1, it2):
            total += (delta := abs(b-f))
            inc = max(inc, abs(b-first)-delta, abs(last-f)-delta)
            if f < b:
                if f > mx:mx = f
                if b < mn:mn = b
            else:
                if b > mx:mx = b
                if f < mn:mn = f
        return total + (inc if (_inc := (mx-mn)*2) < inc else _inc)
20900