Posts

Search

Day 20: Sorting

Objective
Today, we're discussing a simple sorting algorithm called Bubble Sort. Check out the Tutorial tab for learning materials and an instructional video!
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;
        int totalSwaps = 0; 
        for (int i = 0; i < n; i++) {
            int numSwaps = 0;
            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;
                    numSwaps++; 
                    totalSwaps++;
                }
            }
            if (numSwaps == 0) {
                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]);
                break;
            }
        }
    }
    
    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();
    }
}

Posted by