Homework

Write a program that randomly fills in 0s and 1s into an n-by-n matrix, prints the matrix, and finds the rows and columns with the most 1s. (Hint: Use two ArrayLists to store the row and column indices with the most 1s.)

Here is a sample run of the program, printed in the console:

Enter the array size n: 4
The random array is
0011
0011
1101
1010
The largest row index: 2
The largest column index: 2, 3 

import java.util.ArrayList;
import java.util.Scanner;

public class Matrix {
    public static void main(String[] args) {
        // Get matrix size from user
        Scanner scan = new Scanner(System.in);
        System.out.print("Enter the array size n: ");
        int n = scan.nextInt();
        
        // Make the array
        int[][] array = new int[n][n];
        
        // Fill array with random 0s and 1s
        for (int i = 0; i < array.length; i++) {
            for (int j = 0; j < array[i].length; j++) {
                // Generate random 0 or 1
                array[i][j] = (int)(Math.random() * 2);
            }
        }
        
        // Print the array
        System.out.println("The random array is");
        for (int i = 0; i < array.length; i++) {
            for (int j = 0; j < array[i].length; j++) {
                System.out.print(array[i][j]);
            }
            System.out.println();
        }
        
        // Find rows with most 1s
        ArrayList<Integer> rowList = new ArrayList<>();
        int mostOnes = 0;
        
        // Check each row
        for (int i = 0; i < array.length; i++) {
            int count = 0;
            // Count 1s in this row
            for (int j = 0; j < array[i].length; j++) {
                if (array[i][j] == 1) {
                    count = count + 1;
                }
            }
            
            // If we found more 1s than before
            if (count > mostOnes) {
                mostOnes = count;
                rowList.clear();  // Clear old row numbers
                rowList.add(i);   // Add new row number
            }
            // If we found same number of 1s
            else if (count == mostOnes) {
                rowList.add(i);
            }
        }
        
        // Find columns with most 1s
        ArrayList<Integer> colList = new ArrayList<>();
        mostOnes = 0;
        
        // Check each column
        for (int j = 0; j < array[0].length; j++) {
            int count = 0;
            // Count 1s in this column
            for (int i = 0; i < array.length; i++) {
                if (array[i][j] == 1) {
                    count = count + 1;
                }
            }
            
            // If we found more 1s than before
            if (count > mostOnes) {
                mostOnes = count;
                colList.clear();  // Clear old column numbers
                colList.add(j);   // Add new column number
            }
            // If we found same number of 1s
            else if (count == mostOnes) {
                colList.add(j);
            }
        }
        
        // Print results
        System.out.print("The largest row index: ");
        for (int i = 0; i < rowList.size(); i++) {
            System.out.print(rowList.get(i));
            if (i < rowList.size() - 1) {
                System.out.print(", ");
            }
        }
        System.out.println();
        
        System.out.print("The largest column index: ");
        for (int i = 0; i < colList.size(); i++) {
            System.out.print(colList.get(i));
            if (i < colList.size() - 1) {
                System.out.print(", ");
            }
        }
        System.out.println();
    }
}

MatrixAnalysis.main(null);

Enter the array size n: The random array is
000100
110011
011000
100010
000001
101010
The largest row index: 1
The largest column index: 0, 4