Java Program to Find Peak Element of an Array using Binary Search

This is a Java Program to find peak element of an array. A peak element of an array is that element which is greater than its neighbors. The following program uses binary search approach to find a peak element. The time complexity of the following program is O (log n).

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

```
/*
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 * Java Program to Find the peak element of an array using

```
 * Binary Search approach
```
```
 */
```
```
import java.util.Scanner;
```
```
 
```
```
public class PeakElement2    
```
```
{
```

    public static void main(String[] args)

```
    {
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        Scanner scan = new Scanner(System.in);

        System.out.println("Enter size of array");

```
        int N = scan.nextInt();
```
```
        int[] arr = new int[ N ];
```
```
        /* Accept N elements */
```

        System.out.println("Enter "+ N +" elements");

```
        for (int i = 0; i < N; i++)
```
```
            arr[i] = scan.nextInt();
```

        /* Find Peak Elements */

        System.out.print("\nPeak Elements : ");

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        peak(arr);
```
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        System.out.println();
```
```
    } 
```
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    public static void peak(int[] arr)
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    {
```
```
        peak(arr, 0, arr.length - 1);
```
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    }    
```

    public static void peak (int arr[], int low, int high)

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    {
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        int N = arr.length;
```
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        if (high - low < 2)
```
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            return;
```
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        int mid = (low + high) / 2;
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        if (arr[mid] > arr[mid - 1] && arr[mid] > arr[mid + 1])

            System.out.print(arr[mid] +" ");

        /* Recursively find other peak elements */

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        peak (arr, low, mid);
```
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        peak (arr, mid, high);    
```
```
    }        
```
```
}
```

Enter size of array
8
Enter 8 elements
87 63 51 25 40 24 6 1
 
Peak Elements : 40

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