- Difficulty: Hard
- Tags: LeetCode, Hard, Greedy, Array, Binary Search, Dynamic Programming, leetcode-1671, O(nlogn), O(n), Medium, DP
Problem
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) with0 < 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].
Constraints:
3 <= nums.length <= 1000
1 <= nums[i] <= 109
- It is guaranteed that you can make a mountain array out of
nums
.