0845. Longest Mountain in Array

# 845. Longest Mountain in Array#

## 题目 #

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 < B < … 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

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

## 代码 #

``````
package leetcode

func longestMountain(A []int) int {
left, right, res, isAscending := 0, 0, 0, true
for left < len(A) {
if right+1 < len(A) && ((isAscending == true && A[right+1] > A[left] && A[right+1] > A[right]) || (right != left && A[right+1] < A[right])) {
if A[right+1] < A[right] {
isAscending = false
}
right++
} else {
if right != left && isAscending == false {
res = max(res, right-left+1)
}
left++
if right < left {
right = left
}
if right == left {
isAscending = true
}
}
}
return res
}

`````` Apr 8, 2023 Edit this page