Matrix - Sum of elements below and above both diagonal , triangle and more operations on matrix in java


Contents of page >
1) Find sum of elements above diagonal in matrix in java

2) Find sum of elements below diagonal in matrix in java
3) Find sum of both diagonals in matrix in java
4) Find sum of upper triangle in matrix in java
5) Find sum of lower triangle in matrix in java
6) Display in required format in java
7) Matrix Addition in java
8) Matrix Subtraction in java


9) Matrix Multiplication in java
 

10) Matrix Transpose in java


1) Find sum of elements above diagonal in matrix in java
Write a program to Find sum of all elements above diagonal in matrix in java.
Sum of elements above diagonal = 2+3+4+7+8+5= 29




Logic behind finding sum of elements above diagonal in java is:
          //Logic to calculate sum of elements above diagonal.
          int sum=0;
          for (int j = 1; j < columns; j++) {
                 for (int i=j-1 ; i>=0 ; i--) {
                       sum= sum + matrix[i][j];
                 }
                
          }

Example / Full Program/SourceCode in java >
package matrix;
import java.util.Scanner;
/** Copyright (c), AnkitMittal  JavaMadeSoEasy.com */
public class SumOfElementsAboveDiagonal {
   public static void main(String...args) {
         
          Scanner scanner = new Scanner(System.in);
          System.out.print("Enter number of rows/columns in matrix : ");    //rows and columns in matrix must be same.
          int rows = scanner.nextInt();
          int columns=rows;
          int[][] matrix = new int[rows][rows];
         
          System.out.println("Enter the elements in matrix :");
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       matrix[i][j] = scanner.nextInt();
                 }
          }
          //Logic to calculate sum of elements above diagonal.
          int sum=0;
          for (int j = 1; j < columns; j++) {
                 for (int i=j-1 ; i>=0 ; i--) {
                       sum= sum + matrix[i][j];
                 }
                
          }
          System.out.println("\nMatrix is : ");
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       System.out.print(matrix[i][j] + " ");
                 }
                 System.out.println();
          }
          System.out.println("sum of elements above diagonal is: "+sum);
   }
}
/*OUTPUT
Enter number of rows/columns in matrix : 4
Enter the elements in matrix :
1
2
3
4
5
6
7
8
8
7
6
5
4
3
2
1
Matrix is :
1 2 3 4
5 6 7 8
8 7 6 5
4 3 2 1
sum of elements above diagonal is: 29
 
*/


2) Find sum of elements below diagonal in matrix in java
Write a program to Find sum of elements below diagonal in matrix in java
Sum of elements below diagonal = 5+8+7+4+3+2= 29

Logic behind finding sum of elements below diagonal in java is:
          //Logic to calculate sum of elements below diagonal.
          int sum=0;
          for (int i = 1; i < rows; i++) {
                 for (int j=i-1 ; j>=0 ; j--) {
                       sum= sum + matrix[i][j];
                 }
                
          }

Example / Full Program/SourceCode in java >
package matrix;
import java.util.Scanner;
/** Copyright (c), AnkitMittal  JavaMadeSoEasy.com */
public class SumOfElementsBelowDiagonal {
   public static void main(String...args) {
         
          Scanner scanner = new Scanner(System.in);
          System.out.print("Enter number of rows/columns in matrix : ");    //rows and columns in matrix must be same.
          int rows = scanner.nextInt();
          int columns=rows;
          int[][] matrix = new int[rows][rows];
         
          System.out.println("Enter the elements in matrix :");
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       matrix[i][j] = scanner.nextInt();
                 }
          }
         
          //Logic to calculate sum of elements below diagonal.
          int sum=0;
          for (int i = 1; i < rows; i++) {
                 for (int j=i-1 ; j>=0 ; j--) {
                       sum= sum + matrix[i][j];
                 }
                
          }
          System.out.println("\nMatrix is : ");
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       System.out.print(matrix[i][j] + " ");
                 }
                 System.out.println();
          }
          System.out.println("sum of elements below diagonal is: "+sum);
   }
}
/*OUTPUT
Enter number of rows/columns in matrix : 4
Enter the elements in matrix :
1
2
3
4
5
6
7
8
8
7
6
5
4
3
2
1
Matrix is :
1 2 3 4
5 6 7 8
8 7 6 5
4 3 2 1
sum of elements below diagonal is: 29
*/

3) Find sum of both diagonals in matrix in java
Write a program to Find sum of both diagonals in matrix in java.
sum of diagonal1 elements= 1+6+6+1=14,
sum of diagonal2 elements= 4+7+7+4=22
sum of diagonal1 and diagonal2 elements = 14+22= 36


Logic behind finding sum of both diagonals in matrix in java is:
//Logic to calculate sum of diagonal1
          int sumOfDiagonal1=0;
          for (int i = 0, j =0; i< rows && j < columns; i++, j++) {
                 sumOfDiagonal1= sumOfDiagonal1 + matrix[i][j];
                
          }
         
          //Logic to calculate sum of diagonal2
          int sumOfDiagonal2=0;
          for (int i=0,j=columns-1 ; i<rows && j>=0 ; i++, j--) {
                 sumOfDiagonal2= sumOfDiagonal2 + matrix[i][j];
                
          }

Example / Full Program/SourceCode in java >
package matrix;
import java.util.Scanner;
/** Copyright (c), AnkitMittal  JavaMadeSoEasy.com */
public class SumOfBothDiagonals {
   public static void main(String...args) {
         
          Scanner scanner = new Scanner(System.in);
          System.out.print("Enter number of rows/columns in matrix : ");    //rows and columns in matrix must be same.
          int rows = scanner.nextInt();
          int columns=rows;
          int[][] matrix = new int[rows][rows];
         
          System.out.println("Enter the elements in matrix :");
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       matrix[i][j] = scanner.nextInt();
                 }
          }
          //Logic to calculate sum of diagonal1
          int sumOfDiagonal1=0;
          for (int i = 0, j =0; i< rows && j < columns; i++, j++) {
                 sumOfDiagonal1= sumOfDiagonal1 + matrix[i][j];
                
          }
         
          //Logic to calculate sum of diagonal2
          int sumOfDiagonal2=0;
          for (int i=0,j=columns-1 ; i<rows && j>=0 ; i++, j--) {
                 sumOfDiagonal2= sumOfDiagonal2 + matrix[i][j];
                
          }
          System.out.println("\nMatrix is : ");
          for (int i = 0; i < rows; i++) {
             for (int j = 0; j < columns; j++) {
                       System.out.print(matrix[i][j] + " ");
                 }
                 System.out.println();
          }
          System.out.println("sum of diagonal1 elements="+sumOfDiagonal1+", sum of diagonal2 elements ="+ sumOfDiagonal2 );
          System.out.println("sum of diagonal1 and diagonal2 elements is: "+ (sumOfDiagonal1+ sumOfDiagonal2) );
   }
}
/*OUTPUT
Enter number of rows/columns in matrix : 4
Enter the elements in matrix :
1
2
3
4
5
6
7
8
8
7
6
5
4
3
2
1
Matrix is :
1 2 3 4
5 6 7 8
8 7 6 5
4 3 2 1
sum of diagonal1 elements=14, sum of diagonal2 elements =22
sum of diagonal1 and diagonal2 elements is: 36
*/


4) Find sum of upper triangle in matrix in java
Write a program to Find sum of upper triangle in matrix in java.

Sum of upper triangle = 1+2+3+4+6+7+8+6+5+1= 43


Logic behind finding sum of upper triangle in matrix in java is:
          //Logic to calculate sum of upper triangle.
          int sum=0;
          for (int j = 0; j < columns; j++) {
                 for (int i=j ; i>=0 ; i--) {
                       sum= sum + matrix[i][j];
                 }
                
          }

Example / Full Program/SourceCode in java >
package matrix;
import java.util.Scanner;
/** Copyright (c), AnkitMittal  JavaMadeSoEasy.com */
public class SumOfUpperTriangle {
   public static void main(String...args) {
         
          Scanner scanner = new Scanner(System.in);
          System.out.print("Enter number of rows/columns in matrix : ");    //rows and columns in matrix must be same.
          int rows = scanner.nextInt();
          int columns=rows;
          int[][] matrix = new int[rows][rows];
         
          System.out.println("Enter the elements in matrix :");
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       matrix[i][j] = scanner.nextInt();
                 }
          }
         
          //Logic to calculate sum of upper triangle.
          int sum=0;
          for (int j = 0; j < columns; j++) {
                 for (int i=j ; i>=0 ; i--) {
                       sum= sum + matrix[i][j];
                 }
                
          }
          System.out.println("\nMatrix is : ");
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       System.out.print(matrix[i][j] + " ");
                 }
                 System.out.println();
          }
          System.out.println("sum of upper triangle is: "+sum);
   }
}
/*OUTPUT
Enter number of rows/columns in matrix : 4
Enter the elements in matrix :
1
2
3
4
5
6
7
8
8
7
6
5
4
3
2
1
Matrix is :
1 2 3 4
5 6 7 8
8 7 6 5
4 3 2 1
sum of upper triangle is: 43
*/



5) Find sum of lower triangle in matrix in java
Write a program to Find sum of lower triangle in matrix in java.

Sum of lower triangle = 1+5+6+8+7+6+4+3+2+1= 43


Logic behind finding sum of lower triangle in matrix is:
//Logic to calculate sum of lower triangle.
          int sum=0;
          for (int i = 0; i < rows; i++) {
                 for (int j=i ; j>=0 ; j--) {
                       sum= sum + matrix[i][j];
                 }
                
          }


Example / Full Program/SourceCode in java >
package matrix;
import java.util.Scanner;
/** Copyright (c), AnkitMittal  JavaMadeSoEasy.com */
public class SumOfLowerTriangle {
   public static void main(String...args) {
         
          Scanner scanner = new Scanner(System.in);
          System.out.print("Enter number of rows/columns in matrix : ");    //rows and columns in matrix must be same.
          int rows = scanner.nextInt();
          int columns=rows;
          int[][] matrix = new int[rows][rows];
         
          System.out.println("Enter the elements in matrix :");
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       matrix[i][j] = scanner.nextInt();
                 }
          }
         
          //Logic to calculate sum of lower triangle.
          int sum=0;
          for (int i = 0; i < rows; i++) {
                 for (int j=i ; j>=0 ; j--) {
                       sum= sum + matrix[i][j];
                 }
                
          }
          System.out.println("\nMatrix is : ");
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       System.out.print(matrix[i][j] + " ");
                 }
                 System.out.println();
          }
          System.out.println("sum of lower triangle is: "+sum);
   }
}
/*OUTPUT
Enter number of rows/columns in matrix : 4
Enter the elements in matrix :
1
2
3
4
5
6
7
8
8
7
6
5
4
3
2
1
Matrix is :
1 2 3 4
5 6 7 8
8 7 6 5
4 3 2 1
sum of lower triangle is: 43
*/



6) Display in required format in java
Write a program to Display in required format in java


Must read: Level3 programs (advanced) in java.

Logic in java :
   char outputMatrix[][] = new char[columns][rows];
   for (int i = 0; i < rows; i++) {
     for (int j = 0; j < columns; j++)
     outputMatrix[j][i] = matrix[i][j];
   }

Example / Full Program/SourceCode in java >
package matrix;
import java.util.Scanner;
/** Copyright (c), AnkitMittal  JavaMadeSoEasy.com */
public class DisplayInRequiedFormat {
   public static void main(String...args) {
          char matrix[][] =new char[][]{{'A','A','A'},
                                          {'B','B','B'},
                                          {'C','C','C'}};
          int rows=matrix.length;
          int columns=matrix[0].length;
         
          char outputMatrix[][] = new char[columns][rows];
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++)
                       outputMatrix[j][i] = matrix[i][j];
          }
          for (int i = 0; i < columns; i++) {
                 for (int j = 0; j < rows; j++)
                       System.out.print(outputMatrix[i][j] + " ");
                 System.out.println();
          }
   }
}
/*OUTPUT
A B C
A B C
A B C

*/



7) Matrix Addition in java

Hi! we will learn how to add two matrices in java.
Both matrices must have same number of rows and columns in java.

Let’s understand addition of matrices by diagram.



Main logic behind addition is:
          //Subtraction of matrices.
          int[][] resultMatix = new int[rows][columns];
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       resultMatix[i][j] = matrix1[i][j] + matrix2[i][j];
                 }
          }


Example / Full Program/SourceCode in java>
package matrix;
import java.util.Scanner;
/**
* @author AnkitMittal
*/
/** Copyright (c), AnkitMittal  JavaMadeSoEasy.com */
public class MatrixAddition {
   public static void main(String...args) {
          Scanner scanner = new Scanner(System.in);
          System.out.print("Enter number of rows in matrix : "); //rows and columns in matrix1 and matrix2 must be same for addition.
          int rows = scanner.nextInt();
          System.out.print("Enter number of columns in matrix : ");
          int columns = scanner.nextInt();
          int[][] matrix1 = new int[rows][columns];
          int[][] matrix2 = new int[rows][columns];
         
          System.out.println("Enter the elements in first matrix :");
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       matrix1[i][j] = scanner.nextInt();
                 }
          }
          System.out.println("Enter the elements in second matrix :");
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       matrix2[i][j] = scanner.nextInt();
                 }
          }
         
          //addition of matrices.
          int[][] resultMatix = new int[rows][columns];
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       resultMatix[i][j] = matrix1[i][j] + matrix2[i][j];
                 }
          }
          System.out.println("\nFirst matrix is : ");
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       System.out.print(matrix1[i][j] + " ");
                 }
                 System.out.println();
          }
          System.out.println("\nSecond matrix is : ");
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       System.out.print(matrix2[i][j] + " ");
                 }
                 System.out.println();
          }
          System.out.println("\nThe sum of the two matrices is : ");
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       System.out.print(resultMatix[i][j] + " ");
                 }
                 System.out.println();
          }
   }
}
/*OUTPUT
Enter number of rows in matrix : 2
Enter number of columns in matrix : 2
Enter the elements in first matrix :
7
2
5
3
Enter the elements in second matrix :
2
1
3
1
First matrix is :
7 2
5 3
Second matrix is :
2 1
3 1
The sum of the two matrices is :
9 3
8 4
*/



8) Matrix Subtraction in java
Hi! we will learn how to add subtract matrices in java.
Both matrices must have same number of rows and columns in java.

Let’s understand subtraction of matrices by diagram.


Main logic behind subtraction in java is:
          //Subtraction of matrices.
          int[][] resultMatix = new int[rows][columns];
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       resultMatix[i][j] = matrix1[i][j] - matrix2[i][j];
                 }
          }

Example / Full Program/SourceCode  in java>
package matrix;
import java.util.Scanner;
/**
* @author AnkitMittal
*/
/** Copyright (c), AnkitMittal  JavaMadeSoEasy.com */
public class MatrixSubtraction {
   public static void main(String...args) {
          Scanner scanner = new Scanner(System.in);
          System.out.print("Enter number of rows in matrix : "); //rows and columns in matrix1 and matrix2 must be same for subtraction.
          int rows = scanner.nextInt();
          System.out.print("Enter number of columns in matrix : ");
          int columns = scanner.nextInt();
          int[][] matrix1 = new int[rows][columns];
          int[][] matrix2 = new int[rows][columns];
         
          System.out.println("Enter the elements in first matrix :");
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       matrix1[i][j] = scanner.nextInt();
                 }
          }
          System.out.println("Enter the elements in second matrix :");
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       matrix2[i][j] = scanner.nextInt();
                 }
          }
         
          //Subtraction of matrices.
          int[][] resultMatix = new int[rows][columns];
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       resultMatix[i][j] = matrix1[i][j] - matrix2[i][j];
                 }
          }
          System.out.println("\nFirst matrix is : ");
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       System.out.print(matrix1[i][j] + " ");
                 }
                 System.out.println();
          }
          System.out.println("\nSecond matrix is : ");
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       System.out.print(matrix2[i][j] + " ");
                 }
                 System.out.println();
          }
          System.out.println("\nThe subtraction of the two matrices is : ");
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       System.out.print(resultMatix[i][j] + " ");
                 }
                 System.out.println();
          }
   }
}
/*OUTPUT
Enter number of rows in matrix : 2
Enter number of columns in matrix : 2
Enter the elements in first matrix :
7
2
5
3
Enter the elements in second matrix :
2
1
3
1
First matrix is :
7 2
5 3
Second matrix is :
2 1
3 1
The subtraction of the two matrices is :
5 1
2 2
*/


9) Matrix Multiplication in java
Hi! we will learn how to add multiply matrices in java.
In multiplication columns in matrix1 must be equal to rows in matrix2

Let’s understand multiplication of matrices by diagram-
we will find out dot product.





 
Main logic behind multiplication in java is:

        //Multiply matrices
    int[][] productMatrix  = new int[rowsMatrix1][columnsMatrix2];
    for (int i = 0; i < rowsMatrix1; i++) {
      for (int j = 0; j < columnsMatrix2; j++) {
      for (int k = 0; k < columnsMatrix1RowsMatrix2; k++) { //columns in matrix1= rows in matrix2
          productMatrix[i][j]= productMatrix[i][j] + matrix1[i][k] *matrix2[k][j];
        }
         }
  }

Example / Full Program/SourceCode in java >
package matrix;
import java.util.Scanner;
/** Copyright (c), AnkitMittal  JavaMadeSoEasy.com */
public class MatrixMultiplication {
     public static void main(String...args) {
      Scanner scanner = new Scanner(System.in);
     
      System.out.print("Enter number of rows in first matrix : ");
      int rowsMatrix1 = scanner.nextInt();
      System.out.print("Enter number of columns in first matrix / rows in matrix2: ");
      int columnsMatrix1RowsMatrix2 = scanner.nextInt();         //variable name used for understanding convenience, because columns in matrix1 = rows in matrix2
      System.out.print("Enter number of columns in second matrix : ");
      int columnsMatrix2 = scanner.nextInt();
     
      int[][] matrix1 = new int[rowsMatrix1][columnsMatrix1RowsMatrix2];
      int[][] matrix2 = new int[columnsMatrix1RowsMatrix2][columnsMatrix2];
      System.out.println("Enter the first matrix in elements :");
      for (int i = 0; i < matrix1.length; i++) {
          for (int j = 0; j < matrix1[0].length; j++) {
              matrix1[i][j] = scanner.nextInt();
          }
      }
     
      System.out.println("Enter the second matrix elements:");
      for (int i = 0; i < matrix2.length; i++) {
          for (int j = 0; j < matrix2[0].length; j++) {
              matrix2[i][j] = scanner.nextInt();
          }
      }
     
     
      //Multiply matrices
      int[][] productMatrix  = new int[rowsMatrix1][columnsMatrix2];
      for (int i = 0; i < rowsMatrix1; i++) {
          for (int j = 0; j < columnsMatrix2; j++) {
              for (int k = 0; k < columnsMatrix1RowsMatrix2; k++) { //columns in matrix1= rows in matrix2
                 productMatrix[i][j] = productMatrix[i][j] + matrix1[i][k] * matrix2[k][j];
              }
          }
      }
     
                 System.out.println("\nFirst matrix is : ");
                 for (int i = 0; i < rowsMatrix1; i++) {
                       for (int j = 0; j < columnsMatrix1RowsMatrix2; j++) {
                              System.out.print(matrix1[i][j] + " ");
                       }
                       System.out.println();
                 }
                 System.out.println("\nSecond matrix is : ");
                 for (int i = 0; i < columnsMatrix1RowsMatrix2; i++) {
                       for (int j = 0; j < columnsMatrix2; j++) {
                              System.out.print(matrix2[i][j] + " ");
                       }
                       System.out.println();
                 }
                
      System.out.println("\nProduct of matrix1 and matrix2 is");
      for (int i = 0; i < rowsMatrix1; i++) {
          for (int j = 0; j < columnsMatrix2; j++) {
              System.out.print(productMatrix[i][j] + " ");
          }
          System.out.println();
      }
     }
   }
/*OUTPUT
Enter number of rows in first matrix : 2
Enter number of columns in first matrix / rows in matrix2: 3
Enter number of columns in second matrix : 2
Enter the first matrix in elements :
1
2
3
4
5
6
Enter the second matrix elements:
7
8
9
10
11
12
First matrix is :
1 2 3
4 5 6
Second matrix is :
7 8
9 10
11 12
Product of matrix1 and matrix2 is:
58 64
139 154
*/


10) Matrix Transpose in java
Hi! we will learn how to transpose a matrix in java.




Main logic behind transpose in java is:
          //transpose matrix
          int transpose[][] = new int[columns][rows];
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++)
                       transpose[j][i] = matrix[i][j];
          }


Example / Full Program/SourceCode in java >
package matrix;
import java.util.Scanner;
/** Copyright (c), AnkitMittal  JavaMadeSoEasy.com */
public class TransposeMatrix {
   public static void main(String...args) {
          Scanner scanner = new Scanner(System.in);
          System.out.println("Enter number of rows in matrix : ");
          int rows = scanner.nextInt();
          System.out.print("Enter number of columns in matrix : ");
          int columns = scanner.nextInt();
          int matrix[][] = new int[rows][columns];
          System.out.println("Enter the elements in matrix :");
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       matrix[i][j] = scanner.nextInt();
                 }
          }
         
          //transpose matrix
          int transpose[][] = new int[columns][rows];
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++)
                       transpose[j][i] = matrix[i][j];
          }
          System.out.println("\nEntered Matrix is : ");
          for (int i = 0; i < rows; i++) {
                 for (int j = 0; j < columns; j++) {
                       System.out.print(matrix[i][j] + " ");
                 }
                 System.out.println();
          }
         
          System.out.println("\nTranspose of entered matrix is : ");
          for (int i = 0; i < columns; i++) {
                 for (int j = 0; j < rows; j++)
                       System.out.print(transpose[i][j] + " ");
                 System.out.println();
          }
   }
}
/*OUTPUT
Enter number of rows in matrix :
3
Enter number of columns in matrix : 2
Enter the elements in matrix :
1
2
3
4
5
6
Entered Matrix is :
1 2
3 4
5 6
Transpose of entered matrix is :
1 3 5
2 4 6
*/



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