(Easy) Valid Mountain Array - LeetCode

Description:

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 

 

 

Solution:

class Solution {
    public boolean validMountainArray(int[] A) {
        
        if( A==null||A.length<3){
            return false;
        }
        
        int peak=0;
        for(int i = 0; i< A.length-1; i++ ){
            
              
            if(A[i]>A[i+1]){
               System.out.println(A[i]+"  "+A[i+1]); 
                peak = i;
                  break;
            }
            
          
        }
       
        
        for(int i = peak; i<A.length-1; i++){
            
            if(A[i]<=A[i+1]){
                
                return false;
            }
        }
        
        if(peak ==0){
            return false;
        }
        
        return true;
    }
}