CareerCup

private void findPeak(int[] arr) {
for(int i=1;i<arr.length-1;i++) {
if(arr[i-1] < arr[i] && arr[i] > arr[i+1]) {
System.out.println("Peak element "+arr[i]+" and the index of array is "+i);
}
}
}

public static void main(String[] args) {
//int arr[] = {5, 10, 20, 15};
//int arr[] = {10, 20, 15, 2, 23, 90, 67};
int arr[] = {1, 3, 20, 4, 1, 0};
FindPeakElements findPeakElements = new FindPeakElements();
findPeakElements.findPeak(arr);
}

public class PeakElement {

public static void main(String[] args) {
// TODO Auto-generated method stub
int arr[] = { 10, 25, 15, 35, 36, 37 };
System.out.println(findPeakElement(arr, 0, arr.length - 1));
}

private static int findPeakElement(int[] arr, int start, int end) {
// TODO Auto-generated method stub
int mid = (start + end) / 2;

if ((mid == 0 || arr[mid] > arr[mid - 1])
&& (mid == arr.length - 1 || arr[mid] > arr[mid + 1])) {
return arr[mid];
} else if (mid > 0 && (arr[mid] < arr[mid + 1])) {
return findPeakElement(arr, mid + 1, arr.length - 1);
} else {
return findPeakElement(arr, 0, mid - 1);
}
}
}


Reference - geeksforgeeks

Can someone define what is a peak element in an array ?
If I assume it to be the element, before which the elements are smaller than it and after which the elements are larger than it, then will an array have only one peak element ? Or can there be peaks in an array?

Use Binary Search. Time complexity is O(log n).

import java.util.Arrays;

public class ArrayPeakElement {

	public static void main(String[] args) {
		
		int a[] = {1,2,3,4,5,6,1,6,9};
		
		Arrays.sort(a);
		System.out.println("Peak element in the array is" + a[a.length-1]);
		
	}
}