Find Number of Sorted Rows in a Matrix in Java?

Matrices are nothing but a collection of data elements arranged in a rectangular layout that is two-dimensional. In Java, an array with two dimensions can be considered as a matrix.

As per the problem statement the task is to count all the rows in a matrix that are sorted either in strictly increasing order or in strictly decreasing order.

Let’s deep dive into this article, to know how it can be done by using Java programming language.

To show you some instances

Instance-1

Suppose the original matrix is{ 
   { 5, 6, 7, 8 ,
   { 5, 3, 1, 0 },
   { 10, 7, 4, 3 },
   { 13, 7, 8, 21 },
   { 5, 4, 11 ,22 },
   { 11, 2, 3 ,4 }
};

After counting the sorted rows in a matrix, the result index will be:

The sorted rows in a matrix: 3

Instance-2

Suppose the original matrix is{
   { 3, 5, 7, 9 },
   { 5, 3, 1, 8 },
   { 10, 7, 4, 3 },
   { 4, 7, 8, 11 },
   { 0, 4, 11 ,22 },
   { 1, 2, 3 ,0 }
};

After counting the sorted rows in a matrix, the result index will be:

The sorted rows in a matrix: 4

Algorithm

Step 1 − Initialise and declare the matrix

Step 2 −Check the increasing or decreasing order of the rows using a for loop.

Step 3 − Count the total number of rows.

Step 4 − Print the result.

Multiple Approaches

We have provided the solution in different approaches

• By Using Static Initialization of Matrix

• By Using User Defined Method

Let’s see the program along with its output one by one.

Approach-1: By Using Static Initialization of Matrix

In this approach, matrix elements will be initialized in the program. Then as per the algorithm, find the number of sorted rows in a matrix.

Example

public class Main {
   public static void main(String arg[]){
      int m = 6, n = 4; //Initialising and declaring the matrix
      int mat[][] = {
         { 5, 6, 7, 8 },
         { 5, 3, 1, 0 },
         { 10, 7, 4, 3 },
         { 13, 7, 8, 21 },
         { 5, 4, 11 ,22 },
         { 11, 2, 3 ,4 }
      };
      int result = 0; 
      
      // counting from left to right side to count increasing order of rows
      for (int i = 0; i < m; i++) {
        
        //To check if there is any pair of element that are not in increasing order.
         int j;
         for (j = 0; j < n - 1; j++)
         if (mat[i][j + 1] <= mat[i][j])
         break;
         
         //If the loop didn't break then all elements of current row were in increasing order
         if (j == n - 1)
        
        //count of increasing order
         result++;
      }
      
      // counting from right to left side to count decreasing order of rows
      for (int i = 0; i < m; i++) {
         
         //To check if there is any pair of elements that are not in decreasing order.
         int j;
         for (j = n - 1; j > 0; j--)
         if (mat[i][j - 1] <= mat[i][j])
            break;
         if (n > 1 && j == 0)
            result++;
      }
      System.out.println("The sorted rows in a matrix: " + result);
   }
}

Output

The sorted rows in a matrix: 3

Approach-2: By Using User Defined Method

In this approach, matrix elements will be initialized in the program. Then call a user defined method by passing the matrix as parameter and inside the method as per the algorithm find the number of sorted rows in a matrix.

Example

public class Main {
   public static void main(String arg[]){
      
      //Initialising and declaring the matrix
      int m = 6, n = 4;
      int mat[][] = {
         { 3, 5, 7, 9 },
         { 5, 3, 1, 8 },
         { 10, 7, 4, 3 },
         { 4, 7, 8, 11 },
         { 0, 4, 11 ,22 },
         { 1, 2, 3 ,0 }
      };
      
      //calling user defined method
      sort(mat, m, n);
   }
   
   // user defined method
   static void sort(int mat[][], int r, int c){
      
      //Initializing the result
      int result = 0; 
     
     // counting from left to right side to count increasing order of rows
      for (int i = 0; i < r; i++) {
         
         //To check if there are any pairs of elements that are not in increasing order.
         int j;
         for (j = 0; j < c - 1; j++)
         if (mat[i][j + 1] <= mat[i][j])
         break;
         
         //If the loop didn't break then all elements of current row were in increasing order
         if (j == c - 1)
         
         //count of increasing order
         result++;
      }
      
      // counting from right to left side to count decreasing order of rows
      for (int i = 0; i < r; i++) {
        
        //To check if there is any pair of elements that are not in decreasing order.
         int j;
         for (j = c - 1; j > 0; j--)
         if (mat[i][j - 1] <= mat[i][j])
            break;
        
        //If the loop didn't break then all elements of current row were in decreasing order
         if (c > 1 && j == 0)
        
        //count of decreasing order
            result++;
      }
      
      //print the result
      System.out.println("The sorted rows in a matrix: " + result);
   }
}

Ouput

The sorted rows in a matrix: 4

In this article, we explored different approaches to find the number of sorted rows in a matrix by using Java programming language.