Longest Mountain in Array

arraytwo pointersdynamic 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 arr , return the length of the longest subarray, which is a mountain . Return 0 if there is no mountain subarray.

Example 1

Input: arr = [2,1,4,7,3,2,5]
Output: 5
The largest mountain is [1,4,7,3,2] which has length 5.

Example 2

Input: arr = [2,2,2]
Output: 0
There is no mountain.

1 <= arr.length <= 10 ^4

0 <= arr[i] <= 10 ^4

Follow up:

Can you solve it using only one pass?

Can you solve it in O(1) space?

🤔

Medium

Difficulty

Topic Info

ModuleDSA

CategoryArray

Sub-topicTwo Pointers