C Program to Compute the Sum of Diagonals of a Matrix

Here, we will compute the sum of diagonals of a Matrix using the following 3 methods:

1. Using Conditional statements
2. Taking Custom Input from the user whilst using Conditional Statements
3. Using Functions

We will keep the same input in all the mentioned approaches and get an output accordingly.

Input: 

The matrix is 
1 2 3
4 5 6
7 8 9

Output:

Main diagonal elements sum is = 15
Off-diagonal elements sum is = 15 

Explanation: The main diagonals are 1, 5, and 9. So, the sum of the main diagonals is 1+5+9=15. The off diagonals are 3, 5, and 7. So, the sum of the main diagonals is 3+5+7=15

Taking input matrix from the user 

• C

// C Program to Demonstrate the Sum of Diagonals // of a Matrix by taking input from the user #include <stdio.h>    int main() {        int i, j, m = 3, n = 3, a = 0, sum = 0;     int matrix[10][10];          // if both rows and columns are equal then it is     // possible to calculate diagonal sum     if (m == n) {                  // entering the coefficients of the matrix         for (i = 0; i < m; ++i) {                          for (j = 0; j < n; ++j) {                                  scanf("%d", &matrix[i][j]);             }         }         // printing the input matrix         printf("The matrix is \n");                  // iterates number of rows         for (i = 0; i < m; ++i) {                          // iterates number of columns             for (j = 0; j < n; ++j) {                 printf(" %d", matrix[i][j]);             }             printf("\n");         }         for (i = 0; i < m; ++i) {                          // calculating the main diagonal sum             sum = sum + matrix[i][i];                          // calculating the off diagonal sum             a = a + matrix[i][m - i - 1];         }         // printing the result         printf("\nMain diagonal elements sum is = %d\n",sum);         printf("Off-diagonal elements sum is = %d\n", a);     }     else         // if both rows and columns are not equal then it is         // not possible to calculate the sum         printf("not a square matrix\n");     return 0; }

Output: 

The matrix is 
1 2 3
4 5 6
7 8 9
Main diagonal elements sum is = 15
Off-diagonal elements sum is = 15