Question

Write Java program

that takes an integer N from the command line and creates N by N boolean array a[][] such that a[i][j] is true if i and j are relatively prime (have no common factors) and false otherwise. print the output using * to represent true and a space to represent false and include row and column numbers.

(use sieving)

Answer 1

public class RelativePrime {

    public static boolean areRelativePrimes(int n1, int n2) {
        for (int i = 2; i < Math.min(n1, n2); i++) {
            if (n1%i == 0 && n2%i == 0) {
                return false;
            }
        }
        return true;
    }

    public static void main(String[] args) {
        if (args.length > 0) {
            int n = Integer.parseInt(args[0]);
            boolean[][] arr = new boolean[n][n];
            for (int i = 0; i < arr.length; i++) {
                for (int j = 0; j < arr.length; j++) {
                    arr[i][j] = areRelativePrimes(i, j);
                }
            }
            for (int i = 0; i < arr.length; i++) {
                for (int j = 0; j < arr.length; j++) {
                    if (arr[i][j]) {
                        System.out.print("*");
                    } else {
                        System.out.print(" ");
                    }
                }
                System.out.println();
            }
        } else {
            System.out.println("Please provide a number from command line arguments");
        }
    }
}