Bubble Sort

/*
 * Problem : Sort an array in ascending order.
 * Input   : n, then n integers.
 * Output  : The sorted array.
 * Approach: Swap neighbours.
 * Time    : O(n^2)
 * Space   : O(1)
 * Java    : 8 or newer.
 */
import java.util.Scanner;
import java.util.Arrays;
import java.util.stream.Collectors;

public class Main {
    // This method solves the task. It receives the input and returns the answer.
    static int[] solve(int[] a) {
        int n = a.length;

        // Step 1: Repeat the pass n - 1 times. After pass k, the k largest values are at the end.
        for (int pass = 0; pass < n - 1; pass++) {
            boolean swapped = false;

            // Step 2: Compare neighbours. The end part is already sorted, so we skip it.
            for (int i = 0; i < n - 1 - pass; i++) {
                // Step 3: If the left value is bigger, swap the two values.
                if (a[i] > a[i + 1]) {
                    int temporary = a[i];
                    a[i] = a[i + 1];
                    a[i + 1] = temporary;
                    swapped = true;
                }
            }

            // Step 4: No swap in a full pass means the array is sorted. We can stop early.
            if (!swapped) {
                break;
            }
        }
        return a;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int size = scanner.nextInt();
        int[] a = new int[size];
        for (int i = 0; i < size; i++) {
            a[i] = scanner.nextInt();
        }
        System.out.println(Arrays.stream(solve(a)).mapToObj(String::valueOf).collect(Collectors.joining(" ")));
    }
}