leetcode-problemset/leetcode-cn/problem (English)/使数组 K 递增的最少操作次数(English) [minimum-operations-to-make-the-array-k-increasing].html

<p>You are given a <strong>0-indexed</strong> array <code>arr</code> consisting of <code>n</code> positive integers, and a positive integer <code>k</code>.</p>

<p>The array <code>arr</code> is called <strong>K-increasing</strong> if <code>arr[i-k] &lt;= arr[i]</code> holds for every index <code>i</code>, where <code>k &lt;= i &lt;= n-1</code>.</p>

<ul>
	<li>For example, <code>arr = [4, 1, 5, 2, 6, 2]</code> is K-increasing for <code>k = 2</code> because:

	<ul>
		<li><code>arr[0] &lt;= arr[2] (4 &lt;= 5)</code></li>
		<li><code>arr[1] &lt;= arr[3] (1 &lt;= 2)</code></li>
		<li><code>arr[2] &lt;= arr[4] (5 &lt;= 6)</code></li>
		<li><code>arr[3] &lt;= arr[5] (2 &lt;= 2)</code></li>
	</ul>
	</li>
	<li>However, the same <code>arr</code> is not K-increasing for <code>k = 1</code> (because <code>arr[0] &gt; arr[1]</code>) or <code>k = 3</code> (because <code>arr[0] &gt; arr[3]</code>).</li>
</ul>

<p>In one <strong>operation</strong>, you can choose an index <code>i</code> and <strong>change</strong> <code>arr[i]</code> into <strong>any</strong> positive integer.</p>

<p>Return <em>the <strong>minimum number of operations</strong> required to make the array K-increasing for the given </em><code>k</code>.</p>

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

<pre>
<strong>Input:</strong> arr = [5,4,3,2,1], k = 1
<strong>Output:</strong> 4
<strong>Explanation:
</strong>For k = 1, the resultant array has to be non-decreasing.
Some of the K-increasing arrays that can be formed are [5,<u><strong>6</strong></u>,<u><strong>7</strong></u>,<u><strong>8</strong></u>,<u><strong>9</strong></u>], [<u><strong>1</strong></u>,<u><strong>1</strong></u>,<u><strong>1</strong></u>,<u><strong>1</strong></u>,1], [<u><strong>2</strong></u>,<u><strong>2</strong></u>,3,<u><strong>4</strong></u>,<u><strong>4</strong></u>]. All of them require 4 operations.
It is suboptimal to change the array to, for example, [<u><strong>6</strong></u>,<u><strong>7</strong></u>,<u><strong>8</strong></u>,<u><strong>9</strong></u>,<u><strong>10</strong></u>] because it would take 5 operations.
It can be shown that we cannot make the array K-increasing in less than 4 operations.
</pre>

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

<pre>
<strong>Input:</strong> arr = [4,1,5,2,6,2], k = 2
<strong>Output:</strong> 0
<strong>Explanation:</strong>
This is the same example as the one in the problem description.
Here, for every index i where 2 &lt;= i &lt;= 5, arr[i-2] &lt;=<b> </b>arr[i].
Since the given array is already K-increasing, we do not need to perform any operations.</pre>

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

<pre>
<strong>Input:</strong> arr = [4,1,5,2,6,2], k = 3
<strong>Output:</strong> 2
<strong>Explanation:</strong>
Indices 3 and 5 are the only ones not satisfying arr[i-3] &lt;= arr[i] for 3 &lt;= i &lt;= 5.
One of the ways we can make the array K-increasing is by changing arr[3] to 4 and arr[5] to 5.
The array will now be [4,1,5,<u><strong>4</strong></u>,6,<u><strong>5</strong></u>].
Note that there can be other ways to make the array K-increasing, but none of them require less than 2 operations.
</pre>

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

<ul>
	<li><code>1 &lt;= arr.length &lt;= 10<sup>5</sup></code></li>
	<li><code>1 &lt;= arr[i], k &lt;= arr.length</code></li>
</ul>