LeetCode 845: Longest Mountain in Array Solution

Master LeetCode problem 845 (Longest Mountain in Array), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

845. Longest Mountain in Array

Medium

Array Two Pointers Dynamic Programming Enumeration

Problem Explanation

Explanation

To solve this problem, we can iterate through the array and look for potential mountain peaks. Once we find a peak, we can expand to the left and right to find the length of the mountain. We can keep track of the longest mountain found so far and return its length at the end.

Initialize variables maxLen to 0 to store the length of the longest mountain found so far.
Iterate through the array from index 1 to arr.length - 2.
Check if the current element is a peak (arr[i] is greater than both its neighbors).
If it is a peak, expand to the left and right to find the length of the mountain.
Update maxLen if the current mountain length is greater than maxLen.
Return the final maxLen.

Time Complexity: O(N) where N is the number of elements in the array. We iterate through the array once. Space Complexity: O(1) as we are using constant extra space.

Solution Code

class Solution {
    public int longestMountain(int[] arr) {
        int maxLen = 0;
        for (int i = 1; i < arr.length - 1; i++) {
            if (arr[i] > arr[i - 1] && arr[i] > arr[i + 1]) {
                int left = i - 1;
                int right = i + 1;
                while (left > 0 && arr[left] > arr[left - 1]) {
                    left--;
                }
                while (right < arr.length - 1 && arr[right] > arr[right + 1]) {
                    right++;
                }
                maxLen = Math.max(maxLen, right - left + 1);
            }
        }
        return maxLen;
    }
}

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