PascalOptimized

/*

@startuml
class pascalOptimized {
    +main(String[] args) : void
    -printPascalIterative(int rows) : void
}

pascalOptimized ..> java.util.Scanner : uses
@enduml

*/



import java.util.Scanner;

public class PascalOptimized {

    public static void main(String[] args) {
        try (Scanner scan = new Scanner(System.in)) {
            System.out.println("---------- Welcome to Pascal Triangle (Optimized) ----------");
            while (true) {
                int rows;
                while (true) {
                    System.out.print("Please enter a positive integer or 'bye' to quit:");
                    String input = scan.nextLine().trim();
                    if (input.matches("(?i).*(bye|exit|quit).*")) {
                        System.out.println("Goodbye!");
                        return;
                    }
                    if (input.matches("\\d+") && Integer.parseInt(input) > 0) {
                        rows = Integer.parseInt(input);
                        break;
                    } else {
                        System.out.println("Invalid input!");
                    }
                }
                long start = System.currentTimeMillis();
                pascal(rows);
                long end = System.currentTimeMillis();
                long duration = end - start;
                System.out.println("Duration: " + duration + " ms\n");
                while (true) {
                    System.out.println("Do you want to play again? (y/n)");
                    String again = scan.nextLine().trim().toLowerCase();
                    switch (again) {
                        case "n" -> {
                            System.out.println("Program ended. Goodbye!");
                            return;
                        }
                        case "y" -> {
                            break;
                        }
                        default -> {
                            System.out.println("Invalid input.");
                            continue;
                        }
                    }
                    break;
                }
            }
        }
    }

    public static void pascal(int rows) {
        int[][] table = new int[rows][rows];
        int lineMaxWidth = 4 * rows;
        for (int i = 0; i < rows; i++) {
            table[i] = new int[i + 1];
            table[i][0] = table[i][i] = 1;
            for (int j = 1; j < i; j++) {
                table[i][j] = table[i - 1][j - 1] + table[i - 1][j];
            }
            System.out.printf("%" + (lineMaxWidth - 2 * i) + "s", "");
            for (int element : table[i]) {
                System.out.printf("%4d", element);
            }
            System.out.println();
        }
    }
}