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[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.
解题思路
两个指针，确定左山脚，向右寻找右山脚
代码
class Solution:
def longestMountain(self, A: List[int]) -> int:
n = len(A)
res = l = 0
while l + 2 < n:
r = l + 1
if A[l] < A[l + 1]:
while r + 1 < n and A[r] < A[r + 1]:
r += 1
if r < n - 1 and A[r] > A[r + 1]:
while r + 1 < n and A[r] > A[r + 1]:
r += 1
res = max(res, r - l + 1)
else:
r += 1
l = r
return res
