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Java Array Exercises: Find Longest Bitonic Subarray in a given array

Java Array: Exercise-64 with Solution

Write a Java program to find Longest Bitonic Subarray in a given array.

A bitonic subarray is a subarray of a given array where elements are first sorted in increasing order, then in decreasing order. A strictly increasing or strictly decreasing subarray is also accepted as bitonic subarray.

Example:
Input :
nums = { 4, 5, 9, 5, 6, 10, 11, 9, 6, 4, 5 }
Output:
The longest bitonic subarray is [3,9]
Elements of the said sub-array: 5 6 10 11 9 6 4
The length of longest bitonic subarray is 7

Sample Solution:

Java Code:

import java.util.Arrays;
class solution
{
	public static int find_Bitonic_Subarray(int[] nums)
	{
		int[] incre_array = new int[nums.length];
		incre_array[0] = 1;
		for (int i = 1; i < nums.length; i++) {
			incre_array[i] = 1;
			if (nums[i - 1] < nums[i]) {
				incre_array[i] = incre_array[i - 1] + 1;
			}
		}

		int[] decre_array = new int[nums.length];
		decre_array[nums.length - 1] = 1;
		for (int i = nums.length - 2; i >= 0; i--) {
			decre_array[i] = 1;
			if (nums[i] > nums[i + 1]) {
				decre_array[i] = decre_array[i + 1] + 1;
			}
		}

		int lbs_len = 1;
		int start = 0, end = 0;

		for (int i = 0; i < nums.length; i++)
		{
			if (lbs_len < incre_array[i] + decre_array[i] - 1)
			{
				lbs_len = incre_array[i] + decre_array[i] - 1;
				start = i - incre_array[i] + 1;
				end = i + decre_array[i] - 1;
			}
		}

		// print longest bitonic sub-array
		System.out.println("The longest bitonic subarray is [" + start + "," + end + "]");
		System.out.print("Elements of the said sub-array: ");
	    for (int x = start; x <= end; x++)
	     {
			
		  System.out.print(nums[x]+" ");			
		 }	

		System.out.println("\nThe length of longest bitonic subarray is " + lbs_len);

		return lbs_len;
	}

	public static void main(String[] args)
	{
		int[] nums = { 4, 5, 9, 5, 6, 10, 11, 9, 6, 4, 5 };
		System.out.println("\nOriginal array: "+Arrays.toString(nums));
		find_Bitonic_Subarray(nums);
	}
}

Sample Output:

Original array: [4, 5, 9, 5, 6, 10, 11, 9, 6, 4, 5]
The longest bitonic subarray is [3,9]
Elements of the said sub-array: 5 6 10 11 9 6 4 
The length of longest bitonic subarray is 7

Flowchart:

Flowchart: Find Longest Bitonic Subarray in a given array.

Java Code Editor:

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Next: Write a Java program to find maximum difference between two elements in a given array of integers such that smaller element appears before larger element.

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Java: Tips of the Day

Array vs ArrayLists:

The main difference between these two is that an Array is of fixed size so once you have created an Array you cannot change it but the ArrayList is not of fixed size. You can create instances of ArrayLists without specifying its size. So if you create such instances of an ArrayList without specifying its size Java will create an instance of an ArrayList of default size.

Once an ArrayList is full it re-sizes itself. In fact, an ArrayList is internally supported by an array. So when an ArrayList is resized it will slow down its performance a bit as the contents of the old Array must be copied to a new Array.

At the same time, it's compulsory to specify the size of an Array directly or indirectly while creating it. And also Arrays can store both primitives and objects while ArrayLists only can store objects.

Ref: https://bit.ly/3o8L2KH