Write a C program to read elements in a matrix and check whether the matrix is a lower triangular matrix or not. C program to find whether the matrix is lower triangular or not.

1 0 0

4 5 0

7 8 9

Output: Matrix is lower triangular

For any matrix

If arr[i][j] == 0 and j > i then it is a lower triangular matrix.

Happy coding ;)

**Example:**If elements of the matrix are:1 0 0

4 5 0

7 8 9

Output: Matrix is lower triangular

### Required knowledge:

Basic C programming, For loop, Array, Matrix#### Lower triangular matrix

Lower triangular matrix is a special square matrix whose all elements above the main diagonal is zero.### Algorithm to find lower triangular matrix:

To find whether a matrix is lower triangular or not we need to check if all elements above the main diagonal of the matrix is zero.For any matrix

**A**if elements**A**_{ij}= 0 (Where j ≥ i)If arr[i][j] == 0 and j > i then it is a lower triangular matrix.

### Program:

/** * C program to find lower triangular matrix */ #include <stdio.h> int main() { int A[3][3]; int row, col, isLower; /* * Reads elements in matrix from user */ printf("Enter elements in matrix of size 3x3: \n"); for(row=0; row<3; row++) { for(col=0; col<3; col++) { scanf("%d", &A[row][col]); } } /* * Checks whether the matrix is lower triangular matrix */ isLower = 1; for(row=0; row<3; row++) { for(col=0; col<3; col++) { /* * If elements above main diagonal(col>row) * is not equal to zero(A[row][col]!=0) */ if(col>row && A[row][col]!=0) { isLower = 0; } } } /* * If the matrix is lower triangular matrix */ if(isLower == 1) { printf("Matrix is Lower triangular matrix: \n"); /* * Prints elements of lower triangular matrix */ for(row=0; row<3; row++) { for(col=0; col<3; col++) { if(A[row][col]!=0) { printf("%d ", A[row][col]); } } printf("\n"); } } else { printf("Matrix is not a Lower triangular matrix"); } return 0; }

Output

Enter elements in matrix of size 3x3:

1 0 0

4 5 0

7 8 9

Matrix is Lower triangular matrix:

1

4 5

7 8 9

1 0 0

4 5 0

7 8 9

Matrix is Lower triangular matrix:

1

4 5

7 8 9

Happy coding ;)

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