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Java program to check whether a given matrix is Lower Triangular Matrix or not

In this java program, we are reading a matrix and check whether input matrix is Lower Triangular Matrix or not. By IncludeHelp Last updated : December 23, 2023

Problem statement

Given a matrix and we have to check whether it is Lower Triangular Matrixor not?

Lower Triangular Matrix

A matrix is said to be lower matrix if all the elements above the diagonal of the given matrix are zero. So it is necessary that the elements must be zero.

Example

Enter the size of the matrix : 3
Enter an element : 0
Enter an element : 0
Enter an element : 0
Enter an element : 1
Enter an element : 0
Enter an element : 0
Enter an element : 1
Enter an element : 1
Enter an element : 0
*************************
The Matrix is : 
0	0	0	
1	0	0	
1	1	0	
*************************
The matrix is Lower Triangular

Program to check matrix is Lower Triangular Matrix or not in java

import java.util.Scanner;

public class ExArrayLowerMatrix {
  public static void main(String args[]) throws Exception {
    // create object of scanner class
    Scanner sc = new Scanner(System.in);

    // enter the size.
    System.out.print("Enter the size of the matrix : ");

    int m = sc.nextInt();
    int A[][] = new int[m][m];

    // Input the matrix.
    for (int i = 0; i < m; i++) {
      for (int j = 0; j < m; j++) {
        System.out.print("Enter the elements : ");
        A[i][j] = sc.nextInt();
      }
    }

    // printing the matrix.
    System.out.println("*************************");
    System.out.println("The Matrix is : ");
    for (int i = 0; i < m; i++) {
      for (int j = 0; j < m; j++) {
        System.out.print(A[i][j] + "\t");
      }
      System.out.println();
    }

    System.out.println("*************************");

    int p = 0;

    for (int i = 0; i < m; i++) {
      for (int j = i + 1; j < m; j++) {
        // check for lower matrix or not.
        if (A[i][j] != 0) {
          p = 1;
          break;
        }
      }
    }

    // print matrix is lower triangular or not.
    if (p == 0)
      System.out.println("The matrix is Lower Triangular");
    else
      System.out.println("The matrix is not Lower Triangular");
  }
}

Output

First run:
Enter the size of the matrix : 5
Enter an element : 1
Enter an element : 2
Enter an element : 3
Enter an element : 4
Enter an element : 5
Enter an element : 6
Enter an element : 7
Enter an element : 8
Enter an element : 9
Enter an element : 1
Enter an element : 0
Enter an element : 12
Enter an element : 5
Enter an element : 9
Enter an element : 3
Enter an element : 6
Enter an element : 5
Enter an element : 8
Enter an element : 2
Enter an element : 5
Enter an element : 8
Enter an element : 2
Enter an element : 5
Enter an element : 2
Enter an element : 5
*************************
The Matrix is : 
1	2	3	4	5	
6	7	8	9	1	
0	12	5	9	3	
6	5	8	2	5	
8	2	5	2	5	
*************************
The matrix is not Lower Triangular

Second run:
Enter the size of the matrix : 3
Enter an element : 0
Enter an element : 0
Enter an element : 0
Enter an element : 1
Enter an element : 0
Enter an element : 0
Enter an element : 1
Enter an element : 1
Enter an element : 0
*************************
The Matrix is : 
0	0	0	
1	0	0	
1	1	0	
*************************
The matrix is Lower Triangular

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