Given a matrix, we have to find the sum of main and opposite diagonal elements of a matrix using C program.

Program:

The source code to find the sum of the main and opposite diagonal elements is given below. The given program is compiled and executed using GCC compile on UBUNTU 18.04 OS successfully.

// C program to find the sum of main and opposite diagonal elements

#include <stdio.h>

int main()
{
    int Matrix[3][3] = {
        { 9, 8, 7 },
        { 5, 4, 6 },
        { 1, 2, 3 }
    };

    int i, j, sum1 = 0, sum2 = 0;

    printf("Matrix:\n");
    for (i = 0; i < 3; ++i) {
        for (j = 0; j < 3; ++j) {
            printf(" %d", Matrix[i][j]);
        }
        printf("\n");
    }

    for (i = 0; i < 3; ++i) {
        sum1 = sum1 + Matrix[i][i];
        sum2 = sum2 + Matrix[i][3 - i - 1];
    }

    printf("Sum of Main diagonal elements: %d\n", sum1);
    printf("Sum of Opposite diagonal elements: %d\n", sum2);

    return 0;
}

Output:

Matrix:
 9 8 7
 5 4 6
 1 2 3
Sum of Main diagonal elements: 16
Sum of Opposite diagonal elements: 12

Explanation:

Here, we created a 3X3 matrix matrix using the 2D array. Then we find the sum of main and opposite diagonal elements. After that, we printed the Matrix and the sum of diagonals on the console screen.