Longest Mountain in Array

Similar Problems:

Let’s call any (contiguous) subarray B (of A) a mountain if the following properties hold:

B.length >= 3 There exists some 0 < i < B.length - 1 such that B[0] < B[1] < ... B[i-1] < B[i] > B[i+1] > ... > B[B.length - 1] (Note that B could be any subarray of A, including the entire array A.)

Given an array A of integers, return the length of the longest mountain.

Return 0 if there is no mountain.

Example 1:

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

Note:

- 0 <= A.length <= 10000
- 0 <= A[i] <= 10000

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

- Solution:

// Blog link: https://code.dennyzhang.com/longest-mountain-in-array // Basic Ideas: // Find the top of the mountains. Then keep looking both sides // Complexity: Time O(n), Space O(n) func longestMountain(A []int) int { res := 0 for i:=1; i<len(A)-1; i++ { if A[i-1]<A[i] && A[i]>A[i+1] { j, k := i-1, i+1 for j-1>=0 && A[j-1]<A[j] { j-- } for k+1<len(A) && A[k]>A[k+1] { k++ } if k-j+1 > res { res = k-j+1 } } } return res }