leetcode/0845_longest-mountain-in-array/README.md

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 Explanation: The largest mountain is [1,4,7,3,2] which has length 5. 

Example 2:

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

Constraints:

• 1 <= arr.length <= 104
• 0 <= arr[i] <= 104

Follow up:

• Can you solve it using only one pass?
• Can you solve it in O(1) space?