Java Program to Find Peak Element of an Array using Naive Method

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This is a Java Program to find peak element of an array. A peak element of an array is that element which is not smaller than its neighbors. Consider only one neighbour for corner elements. The time complexity of the following program is O (n).

Brute Force Algorithm is as follows :

for i in range (n) :
    if A[i - 1] <= A[i] >= A[i + 1] :
        print A[i]
    end if
end for

Here is the source code of the Java program to find peak element of an array. The Java program is successfully compiled and run on a Windows system. The program output is also shown below.

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  1. /*
  2.  *    Java Program to Find the peak element of an array O(n) time (Naive Method)
  3.  */
  4.  
  5. import java.util.Scanner;
  6.  
  7. public class PeakElement1
  8. {
  9.     public static void main(String[] args)
  10.     {    
  11.         Scanner scan = new Scanner(System.in);
  12.         System.out.println("Enter size of array");
  13.         int N = scan.nextInt();
  14.         int[] arr = new int[N + 2];
  15.         /* set corner values to -infinity */
  16.         arr[0] = Integer.MIN_VALUE;
  17.         arr[N + 1] = Integer.MIN_VALUE;
  18.  
  19.         /* Accept N elements */
  20.         System.out.println("Enter "+ N +" elements");
  21.         for (int i = 1; i <= N; i++)
  22.             arr[i] = scan.nextInt();
  23.  
  24.         /* Find All Peak Elements */
  25.         System.out.println("\nAll Peak Elements : ");
  26.         for (int i = 1; i <= N; i++)
  27.             if (arr[i - 1] <= arr[i] && arr[i] >= arr[i + 1])
  28.                 System.out.println(arr[i] +" at position "+ i);
  29.  
  30.         System.out.println();    
  31.     }         
  32. }

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Enter size of array
6
Enter 6 elements
1 2 5 5 4 1
 
All Peak Elements :
5 at position 3
5 at position 4
 
 
 
Enter size of array
7
Enter 7 elements
6 24 15 2 23 99 67
 
All Peak Elements :
24 at position 2
99 at position 6
 
 
 
Enter size of array
10
Enter 10 elements
10 9 8 24 8 7 97 28 17 63
 
All Peak Elements :
10 at position 1
24 at position 4
97 at position 7
63 at position 10

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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