Peak element Java

PROGRAM TO FIND THE PEAK ELEMENT IN AN ARRAY

An array element is a peak if it is NOT smaller than its neighbours. For corner elements, we need to consider only one neighbour.

import java.util.*;

import java.lang.*;

import java.io.*;

  

class PeakElement {

    // A binary search based function

    // that returns index of a peak element

    static int findPeakUtil( int arr[], int low, int high,         int n)

    {

        // Find index of middle element

        // (low + high)/2

        int mid = low + (high - low) / 2;

  

        // Compare middle element with its

        // neighbours (if neighbours exist)

        if ((mid == 0 || arr[mid - 1] <= arr[mid])

            && (mid == n - 1 || arr[mid + 1] <= arr[mid]))

            return mid;

  

        // If middle element is not peak

        // and its left neighbor is

        // greater than it, then left half

        // must have a peak element

        else if (mid > 0 && arr[mid - 1] > arr[mid])

            return findPeakUtil(arr, low, (mid - 1), n);

  

        // If middle element is not peak

        // and its right neighbor

        // is greater than it, then right

        // half must have a peak

        // element

        else

            return findPeakUtil(

                arr, (mid + 1), high, n);

    }

  

    // A wrapper over recursive function

    // findPeakUtil()

    static int findPeak(int arr[], int n)

    {

        return findPeakUtil(arr, 0, n - 1, n);

    }

  

    // Driver method

    public static void main(String[] args)

    {

        int arr[] = { 1, 3, 20, 4, 1, 0 };

        int n = arr.length;

        System.out.println(

            "Index of a peak point is " + findPeak(arr, n));

    }

}

OUTPUT

Index of a peak point is 2

CREDITS:  https://www.geeksforgeeks.org/find-a-peak-in-a-given-array/