845. Longest Mountain in Array

 

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.

 

class Solution {

public int longestMountain(int[] arr) {

int base = 0;

int ans = 0;

int n = arr.length;

while(base < arr.length){

int end = base;

if(end + 1 < n && arr[end] < arr[end + 1]){

while(end + 1 < n && arr[end] < arr[end + 1]){

end++;

}

if(end + 1 < n && arr[end] > arr[end+1]){

while(end + 1 < n && arr[end] > arr[end+1]){

end++;

}

ans = Math.max(ans,end - base + 1);

}

}

base = Math.max(end,base + 1);

}

return ans;

}

}