1671. Minimum Number of Removals to Make Mountain Array

https://leetcode.com/problems/minimum-number-of-removals-to-make-mountain-array

Description

You may recall that an array arr is a mountain array if and only if:

• arr.length >= 3

• There exists some index i (0-indexed) with 0 < i < arr.length - 1 such that:

  • arr[0] < arr[1] < ... < arr[i - 1] < arr[i]

  • arr[i] > arr[i + 1] > ... > arr[arr.length - 1]

Given an integer array nums​​​, return the minimum number of elements to remove to make nums*​​​*a mountain array.

Example 1:

**Input:** nums = [1,3,1]
**Output:** 0
**Explanation:** The array itself is a mountain array so we do not need to remove any elements.

Example 2:

**Input:** nums = [2,1,1,5,6,2,3,1]
**Output:** 3
**Explanation:** One solution is to remove the elements at indices 0, 1, and 5, making the array nums = [1,5,6,3,1].

Example 3:

**Input:** nums = [4,3,2,1,1,2,3,1]
**Output:** 4

Example 4:

**Input:** nums = [1,2,3,4,4,3,2,1]
**Output:** 1

Constraints:

• 3 <= nums.length <= 1000

• 1 <= nums[i] <= 109

• It is guaranteed that you can make a mountain array out of nums.

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