Class Matrix

Lecture 20 - 2D Arrays/src/Matrix.java:3–86

import java.util.Scanner;

public class Matrix {
    static void printMatrix(int[][] matrix){
        for(int i = 0; i < matrix.length; i++){
            for(int j = 0; j < matrix[i].length; j++){
                System.out.print(matrix[i][j] + " ");
            }
            System.out.println();
        }
    }

    static void multiply(int[][] a, int r1, int c1, int[][] b, int r2, int c2){
            if(c1 != r2){
                System.out.println("Multiplication not possible - wrong dimension");
                return;
            }

            int[][] mul = new int[r1][c2];

            for(int i = 0; i < r1; i++){ // row number
                for(int j = 0; j < c2; j++){ //column number
                    for(int k = 0; k < c1; k++){
                        /*
                          i = 1, j = 0
                          mul[i][j] = ith row of a * jth col of b
                        */
                        mul[i][j] += (a[i][k] * b[k][j]);
                    }
                }
            }

            System.out.println("Multiplication of 2 matrices");
            printMatrix(mul);
    }

    static void add(int[][] a, int r1, int c1, int[][] b, int r2, int c2){
        if(r1 != r2 || c1 != c2){
            System.out.println("Wrong Input - Addition not possible");
            return;
        }

        int[][] sum = new int[r1][c1];

         for(int i = 0; i < r1; i++){ //row number
            for(int j = 0; j < c1; j++){ //column number
                sum[i][j] = a[i][j] + b[i][j];
            }
        }
        System.out.println("Sum of matrix 1 and matrix 2");
        printMatrix(sum);
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter number of rows and columns of matrix 1");
        int r1 = sc.nextInt();
        int c1 = sc.nextInt();
        int[][] a = new int[r1][c1];
        System.out.println("Enter matrix values");