Day 20: Sorting - HackerRank 30 days of code solution

Objective
Today, we're discussing a simple sorting algorithm called Bubble Sort.

---

Consider the following version of Bubble Sort:

for (int i = 0; i < n; i++) {
    // Track number of elements swapped during a single array traversal
    int numberOfSwaps = 0;
    
    for (int j = 0; j < n - 1; j++) {
        // Swap adjacent elements if they are in decreasing order
        if (a[j] > a[j + 1]) {
            swap(a[j], a[j + 1]);
            numberOfSwaps++;
        }
    }
    
    // If no elements were swapped during a traversal, array is sorted
    if (numberOfSwaps == 0) {
        break;
    }
}

Task
Given an array, , of size  distinct elements, sort the array in ascending order using the Bubble Sort algorithm above. Once sorted, print the following  lines:

1. Array is sorted in numSwaps swaps.
   where  is the number of swaps that took place.
2. First Element: firstElement
   where  is the first element in the sorted array.
3. Last Element: lastElement
   where  is the last element in the sorted array.

Hint: To complete this challenge, you will need to add a variable that keeps a running tally of all swaps that occur during execution.

Input Format

The first line contains an integer, , denoting the number of elements in array .
The second line contains  space-separated integers describing the respective values of .

Constraints

• , where .

Output Format

Print the following three lines of output:

1. Array is sorted in numSwaps swaps.
   where  is the number of swaps that took place.
2. First Element: firstElement
   where  is the first element in the sorted array.
3. Last Element: lastElement
   where  is the last element in the sorted array.

Sample Input 0

3
1 2 3

Sample Output 0

Array is sorted in 0 swaps.
First Element: 1
Last Element: 3

Explanation 0

The array is already sorted, so  swaps take place and we print the necessary  lines of output shown above.

Sample Input 1

3
3 2 1

Sample Output 1

Array is sorted in 3 swaps.
First Element: 1
Last Element: 3

Explanation 1

The array  is not sorted, so we perform the following  swaps:

At this point the array is sorted and we print the necessary  lines of output shown above.

Solution :

import java.util.Scanner;

public class Solution {

    private static int[] array;

    private static void bubbleSort() {

        int n = array.length;

        

        // Number of swaps for all array iterations

        int totalSwaps = 0; 

        for (int i = 0; i < n; i++) {

            // Track if any swap was made

            boolean swapped = false;

            

            for (int j = 0; j < array.length - 1; j++) {

                if (array[j] > array[j + 1]) {

                    int tmp = array[j];

                    array[j] = array[j + 1];

                    

                    array[j + 1] = tmp;

                    swapped = true; 

                    totalSwaps++;

                }

            }

            // Terminate loop if array is sorted

            if (!swapped) {

                break;

            }

        }

        

        // Print answer

        System.out.printf("Array is sorted in %d swaps.\n", totalSwaps);

        System.out.printf("First Element: %d\n", array[0]);

        System.out.printf("Last Element: %d\n", array[n - 1]);

    }

    

    public static void main(String[] args){

        Scanner in = new Scanner(System.in);

        int n = in.nextInt();

        array = new int[n];

        for (int i = 0; i < n; i++) {

            array[i] = in.nextInt();

        }

        in.close();

        bubbleSort();

    }

}