C program to check whether a matrix is Identity matrix

Write a C program to read elements in a matrix and check whether matrix is an Identity matrix or not. C program for finding Identity matrix.

Example: If elements of a 3x3 matrix are:
1 0 0
0 1 0
0 0 1

Output: It is an Identity matrix.

Required knowledge:

Basic C programming, For loop, Array, Matrix

Identity Matrix:

Identity matrix is a special square matrix whose main diagonal elements is equal to 1 and other elements are 0. Identity matrix is also known as unit matrix.
Identity matrix

Algorithm to check Identity matrix:

For checking a matrix A we need to ensure that
If i = j then Aij must be equal to 1.
Else Aij must be equal to 0. (Where 1 ≤ i ≤ m and 1 ≤ j ≤ n)

Program:

/**
 * C program to check whether a matrix is Identity matrix or not
 */

#include <stdio.h>

int main()
{
    int A[3][3];
    int row, col, isIdentity;

    /*
     * 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 it is Identity matrix or not
     */
    isIdentity = 1;
    for(row=0; row<3; row++)
    {
        for(col=0; col<3; col++)
        {

            if(row==col && A[row][col]!=1)
            {
                /* If elements of main diagonal is not equal to 1 */
                isIdentity = 0;
            }
            else if(row!=col && A[row][col]!=0)
            {
                /* If other elements than main diagonal is not equal to 0 */
                isIdentity = 0;
            }
        }
    }

    /*
     * If it is an Identity matrix
     */
    if(isIdentity==1)
    {
        printf("\nThe given matrix is an Identity Matrix.\n");

        /*
         * Prints the Identity matrix
         */
        for(row=0; row<3; row++)
        {
            for(col=0; col<3; col++)
            {
                printf("%d ", A[row][col]);
            }

            printf("\n");
        }
    }
    else
    {
        printf("The given matrix is not Identity Matrix");
    }

    return 0;
} 

Output
X
_
Enter elements in matrix of size 3x3:
1 0 0
0 1 0
0 0 1

The given matrix is an Identity Matrix.
1 0 0
0 1 0
0 0 1

Happy coding ;)


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