Java Program to Count all the Sorted Rows in a Matrix

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In the previous article, we have seen Java Program to Find the Row having Maximum 0’s in a Binary Matrix

In this article we are going to see how we can count the sorted rows of a matrix in JAVA language.

Java Program to Count all the Sorted Rows in a Matrix

A 3*3 Matrix is having 3 rows and 3 columns where this 3*3 represents the dimension of the matrix. Means there are 3*3 i.e. total 9 elements in a 3*3 Matrix.

Let’s understand it in more simpler way.

                   | A00   A01   A02 |
Matrix A =  | A10   A11   A12 |
                   | A20   A21   A22 | 3*3
  • Matrix A represents a 3*3 matrix.
  • ‘A‘ represents the matrix element
  • ‘Aij‘ represents the matrix element at it’s matrix position/index.
  • ‘i‘ represents the row index
  • ‘j‘ represents the column index
  • Means A00=Aij  where i=0 and j=0,  A01=aij where i=0 and j=1 and like this.
  • Here we have started row value from 0 and column value from 0.

Let’s see different ways to count all the sorted rows in a matrix.

Method-1: Java Program to Count all the Sorted Rows in a Matrix By Static Initialization of Array Elements

Approach:

  • Initialize an array of size 3×3 with values.
  • Show the array to the user.
  • Use two for loops to iterate the row and column index.
  • Check if the rows are in increasing order, if yes then increment the result variable.
  • Check if the rows are in decreasing order, if yes then increment the result variable.
  • Print the result.

Program:

import java.util.Scanner;
public class Matrix
{
    public static void main(String args[])
    {
        //Scanner class to take input
        Scanner scan = new Scanner(System.in);

        // Initializing the 3X3 matrix i.e. 2D array
        int arr[][] = {{1,2,3},{6,5,4},{7,9,8}};
        int row, col ;

        System.out.print("The matrix elements are : ");
        printMatrix(arr);
        System.out.println("\nThe number of sorted rows in the matrix are : "+sortedRows(arr));
        
    }

    // Method to print the matrix
    static void printMatrix(int arr[][])
    {
        int row, col;
        // Loop to print the elements
        for(row=0;row<3;row++)
        {
            // Used for formatting
            System.out.print("\n");
            for(col=0;col<3;col++)
            {
                System.out.print(arr[row][col]+" ");
            }
        }
    }

    //sortedRows() method to find the number rows in sorted order
    static int sortedRows(int arr[][])
    {
        // Variable to store result
        int res = 0,row,col;
        
        // Starts from left side of the matrix
        for(row=0;row<3;row++)
        {
            for(col=0;col<2;col++)
            // Checks if the elements are not in increasing order
                if(arr[row][col+1]<=arr[row][col])
                    break;
            // If the row is sorted increments the result
            if(col==2)
                res++;
        }
        
        // Starts from right side of the matrix
        for(row=0;row<3;row++)
        {
            for(col=2;col>0;col--)
            // Checks if the elements are not in decreasing order
                if(arr[row][col-1]<=arr[row][col])
                    break;
            if(col==0)
                res++;
        }
        return res;
    }

}

Output:

The matrix elements are : 
1 2 3 
6 5 4 
7 9 8 
The number of sorted rows in the matrix are : 2

Method-2: Java Program to Count all the Sorted Rows in a Matrix By Dynamic Initialization of Array Elements

Approach:

  • Initialize an array of size 3×3.
  • Ask the user for input.
  • Use two for loops to iterate the rows and columns to input the array elements.
  • Show the array to the user.
  • Use two for loops to iterate the row and column index
  • Check if the rows are in increasing order, if yes then increment the result variable.
  • Check if the rows are in decreasing order, if yes then increment the result variable.
  • Print the result.

Program:

import java.util.Scanner;
public class matrix
{
    public static void main(String args[])
    {
        //Scanner class to take input
        Scanner scan = new Scanner(System.in);

        // Initializing the 3X3 matrix i.e. 2D array
        int arr[][] = new int[3][3];
        int row, col ;

        System.out.print("Enter the 3x3 matrix elements :");
        // Loop to take user input
        for(row=0;row<3;row++)
            for(col=0;col<3;col++)
                arr[row][col] = scan.nextInt();

        System.out.print("The matrix elements are:");
        printMatrix(arr);
        System.out.println("\nThe number of sorted rows in the matrix are: "+sortedRows(arr));
        
    }

    // Function to print the matrix
    static void printMatrix(int arr[][])
    {
        int row, col;
        // Loop to print the elements
        for(row=0;row<3;row++)
        {
            // Used for formatting
            System.out.print("\n");
            for(col=0;col<3;col++)
            {
                System.out.print(arr[row][col]+" ");
            }
        }
    }

    static int sortedRows(int arr[][])
    {
        // Variable to store result
        int res = 0,row,col;
        // Starts from left side of the matrix
        for(row=0;row<3;row++)
        {
            for(col=0;col<2;col++)
            // Checks if the elements are not in increasing order
                if(arr[row][col+1]<=arr[row][col])
                    break;
            // If the row is sorted increments the result
            if(col==2)
                res++;
        }
        // Starts from right side of the matrix
        for(row=0;row<3;row++)
        {
            for(col=2;col>0;col--)
            // Checks if the elements are not in decreasing order
                if(arr[row][col-1]<=arr[row][col])
                    break;
            if(col==0)
                res++;
        }
        return res;
    }

}


Output:

Enter the 3x3 matrix elements :The matrix elements are: 1 2 3 4 5 6 9 8 7
1 2 3 
4 5 6 
9 8 7 
The number of sorted rows in the matrix are: 3

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