941. Valid Mountain Array
https://leetcode.com/problems/valid-mountain-array/
Given an array A of integers, return true if and only if it is a valid mountain array.
Recall that A is a mountain array if and only if:
A.length >= 3- There exists some
iwith0 < i < A.length - 1such that:A[0] < A[1] < ... A[i-1] < A[i]A[i] > A[i+1] > ... > A[A.length - 1]
Example 1:
Input: [2,1] Output: false
Example 2:
Input: [3,5,5] Output: false
Example 3:
Input: [0,3,2,1] Output: true
Note:
0 <= A.length <= 100000 <= A[i] <= 10000
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| class Solution { | |
| public boolean validMountainArray(int[] A) { | |
| if (A == null || A.length < 3) { | |
| return false; | |
| } | |
| int i = 0, N = A.length; | |
| while (i + 1 < N && A[i] < A[i + 1]) { | |
| i++; | |
| } | |
| if (i == 0 || i == A.length - 1) { | |
| return false; | |
| } | |
| while (i + 1 < N && A[i] > A[i + 1]) { | |
| i++; | |
| } | |
| return i == N - 1; | |
| } | |
| } |
