LeetCode [941] Valid Mountain Array

 941. Valid Mountain Array

Easy

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 i with 0 < i < A.length - 1 such 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:

1. 0 <= A.length <= 10000
2. 0 <= A[i] <= 10000 

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class Solution { public boolean validMountainArray(int[] A) { int n = A.length; if(n<3 || A[0]>=A[1]) return false; int i = 1; boolean foundMountain = false; while(i<n){ if(A[i]==A[i-1]) return false; if(!foundMountain){ if(A[i]>A[i-1]){ i++; }else{//A[i]<A[i-1], A[i-1] is mountain foundMountain = true; i++; } }else{ if(A[i]<A[i-1]){ i++; }else{ return false; } } } return true; } }