Minimum Number of Removals to Make Mountain Array

arraybinary searchdynamic programming

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
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
One solution is to remove the elements at indices 0, 1, and 5, making the array nums = [1,5,6,3,1].

3 <= nums.length <= 1000

1 <= nums[i] <= 10 ^9

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

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Hard

Difficulty

Topic Info

ModuleDSA

CategoryArray

Sub-topicBinary Search