Matrix Class

Lab Java Advanced 30 points

Write an immutable Matrix class with add, multiply, transpose and toString. Read two 2×2 matrices and print A+B, A×B and Aᵀ separated by -- lines.

Input

Four lines: two rows of A, two rows of B.

Output

The three results.

Example

Input

Output

Sample input available Sample output available

Editor

Java

Hints

Each operation builds and returns a new Matrix.

Solution explanation

Immutable value classes are easy to reason about: an operation never changes its inputs.

Show solution

import java.util.Scanner;

final class Matrix {
    private final int[][] m;

    Matrix(int[][] m) {
        this.m = m;
    }

    Matrix add(Matrix o) {
        int[][] r = new int[m.length][m[0].length];
        for (int i = 0; i < m.length; i++)
            for (int j = 0; j < m[0].length; j++)
                r[i][j] = m[i][j] + o.m[i][j];
        return new Matrix(r);
    }

    Matrix multiply(Matrix o) {
        int[][] r = new int[m.length][o.m[0].length];
        for (int i = 0; i < m.length; i++)
            for (int j = 0; j < o.m[0].length; j++)
                for (int k = 0; k < o.m.length; k++)
                    r[i][j] += m[i][k] * o.m[k][j];
        return new Matrix(r);
    }

    Matrix transpose() {
        int[][] r = new int[m[0].length][m.length];
        for (int i = 0; i < m.length; i++)
            for (int j = 0; j < m[0].length; j++)
                r[j][i] = m[i][j];
        return new Matrix(r);
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < m.length; i++) {
            for (int j = 0; j < m[i].length; j++) {
                sb.append(j > 0 ? " " : "").append(m[i][j]);
            }
            if (i < m.length - 1) sb.append('\n');
        }
        return sb.toString();
    }
}

public class Main {
    static Matrix read(Scanner sc) {
        int[][] m = new int[2][2];
        for (int i = 0; i < 2; i++)
            for (int j = 0; j < 2; j++)
                m[i][j] = sc.nextInt();
        return new Matrix(m);
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Matrix a = read(sc), b = read(sc);
        System.out.println(a.add(b));
        System.out.println("--");
        System.out.println(a.multiply(b));
        System.out.println("--");
        System.out.println(a.transpose());
    }
}

Output

Answer