C program to find determinant of a matrix

Write a C program to read elements in a matrix and find determinant of the given matrix. C program to find determinant of a 2x2 matrix and 3x3 matrix.

Example: If elements of a 2x2 matrix are:
1 2
3 4
Output: Determinant of the matrix = -2

Required knowledge:

Basic C programming, For loop, Array, Matrix

Determinant:

The Determinant of a matrix is a special number that can be calculated from the elements of a square matrix. The determinant of a matrix A is denoted by det (A), det A or |A|.

Read more facts about determinants and formulas to calculate determinants on Math is Fun.

Program to calculate determinant of 2x2 matrix:

/**
 * C program to find determinant of 2x2 matrix
 */

#include <stdio.h>

int main()
{
    int A[2][2];
    int row, col;
    long det;

    /*
     * Reads elements in matrix A from user
     */
    printf("Enter elements in matrix of size 2x2: \n");
    for(row=0; row<2; row++)
    {
        for(col=0; col<2; col++)
        {
            scanf("%d", &A[row][col]);
        }
    }

    /*
     * det(A) = ad - bc
     * a = A[0][0], b = A[0][1], c = A[1][0], d = A[1][1]
     */
    det = (A[0][0] * A[1][1]) - (A[0][1] * A[1][0]);

    printf("Determinant of matrix A = %ld", det);

    return 0;
} 

Program to calculate determinant of 3x3 matrix:

/**
 * C program to find determinant of 3x3 matrix
 */

#include <stdio.h>

int main()
{
    int A[3][3];
    int row, col;
    int a, b, c, d, e, f, g, h, i;
    long det;

    /*
     * Reads elements in matrix A 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]);
        }
    }

    /*
     * Used as a temporary variables to make calculation easy
     * |         |
     * | a  b  c |
     * | d  e  f |
     * | g  h  i |
     * |         |
     */
    a = A[0][0];
    b = A[0][1];
    c = A[0][2];
    d = A[1][0];
    e = A[1][1];
    f = A[1][2];
    g = A[2][0];
    h = A[2][1];
    i = A[2][2];

    /*
     * det(A) = a(ei - fh) - b(di - fg) + c(dh - eg)
     */
    det = (a*(e*i - f*h)) - (b*(d*i - f*g)) + (c*(d*h - e*g));

    printf("Determinant of matrix A = %ld", det);

    return 0;
} 

Happy coding ;)