**Question:**

Write a Program in Java to input a 2-D square matrix and check whether it is a Lower Triangular Matrix or not.

**Lower Triangular Matrix :** A Lower Triangular matrix is a square matrix in which all the entries above the main diagonal (↘) are zero. The entries below or on the main diagonal themselves may or may not be zero.

**Example:**

**Solution:**

/** * The class LowerTriangularMatrix inputs a Matrix and checks whether it is a Lower Triangular Matrix or not * @author : www.guideforschool.com * @Program Type : BlueJ Program - Java */ import java.util.*; class LowerTriangularMatrix { public static void main(String args[])throws Exception { Scanner sc=new Scanner(System.in); System.out.print("Enter the size of the matrix : "); int m=sc.nextInt(); int A[][]=new int[m][m]; /* Inputting the matrix */ for(int i=0;i<m;i++) { for(int j=0;j<m;j++) { System.out.print("Enter an element : "); 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++) { /* Checking that the matrix is Lower Triangular or not */ if(A[i][j]!=0) // All elements above the diagonal must be zero { p=1; break; } } } if(p==0) System.out.println("The matrix is Lower Triangular"); else System.out.println("The matrix is not Lower Triangular"); } }

**Output:**

Enter the size of the matrix : 4

Enter an element : 5

Enter an element : 0

Enter an element : 0

Enter an element : 0

Enter an element : 3

Enter an element : 1

Enter an element : 0

Enter an element : 0

Enter an element : 4

Enter an element : 9

Enter an element : 4

Enter an element : 0

Enter an element : 6

Enter an element : 8

Enter an element : 7

Enter an element : 2

*************************

The Matrix is :

5 0 0 0

3 1 0 0

4 9 4 0

6 8 7 2

*************************

The matrix is Lower Triangular

Awsome logics ?

nice and fantastic job.