leetcode-problemset/leetcode/problem/minimum-number-of-operations-to-make-all-array-elements-equal-to-1.html

<p>You are given a <strong>0-indexed</strong>&nbsp;array <code>nums</code> consisiting of <strong>positive</strong> integers. You can do the following operation on the array <strong>any</strong> number of times:</p>

<ul>
	<li>Select an index <code>i</code> such that <code>0 &lt;= i &lt; n - 1</code> and replace either of&nbsp;<code>nums[i]</code> or <code>nums[i+1]</code> with their gcd value.</li>
</ul>

<p>Return <em>the <strong>minimum</strong> number of operations to make all elements of </em><code>nums</code><em> equal to </em><code>1</code>. If it is impossible, return <code>-1</code>.</p>

<p>The gcd of two integers is the greatest common divisor of the two integers.</p>

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

<pre>
<strong>Input:</strong> nums = [2,6,3,4]
<strong>Output:</strong> 4
<strong>Explanation:</strong> We can do the following operations:
- Choose index i = 2 and replace nums[2] with gcd(3,4) = 1. Now we have nums = [2,6,1,4].
- Choose index i = 1 and replace nums[1] with gcd(6,1) = 1. Now we have nums = [2,1,1,4].
- Choose index i = 0 and replace nums[0] with gcd(2,1) = 1. Now we have nums = [1,1,1,4].
- Choose index i = 2 and replace nums[3] with gcd(1,4) = 1. Now we have nums = [1,1,1,1].
</pre>

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

<pre>
<strong>Input:</strong> nums = [2,10,6,14]
<strong>Output:</strong> -1
<strong>Explanation:</strong> It can be shown that it is impossible to make all the elements equal to 1.
</pre>

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

<ul>
	<li><code>2 &lt;= nums.length &lt;= 50</code></li>
	<li><code>1 &lt;= nums[i] &lt;= 10<sup>6</sup></code></li>
</ul>

<p>&nbsp;</p>
<p><b>Follow-up:</b></p>

<p>The <code>O(n)</code> time complexity&nbsp;solution works, but could you find an <code>O(1)</code> constant time complexity solution?</p>