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].

?

Constraints:

• 3 <= nums.length <= 1000

• 1 <= nums[i] <= 109

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

  Hint1：Think the opposite direction instead of minimum elements to remove the maximum mountain subsequence

  Hint2：Think of LIS it's kind of close

  .

分別從2個(gè)方向求最大遞增數(shù)列的長(zhǎng)度，然后最終匯總，求最值就行了。。

沒(méi)想到啊，我也能解決hard級(jí)別的題目了。。。，多虧上一道題了；

Runtime:?49 ms, faster than?81.64%?of?Java?online submissions for?Minimum Number of Removals to Make Mountain Array.

Memory Usage:?42.2 MB, less than?76.33%?of?Java?online submissions for?Minimum Number of Removals to Make Mountain Array.