Example: Sum of Both Diagonals with Overlap Handling in C

// Sum of Both Diagonals with Overlap Handling
#include <stdio.h>

int main() {
    // Step 1: Define the square matrix and its size
    int matrix[3][3] = {
        {1, 2, 3},
        {4, 5, 6},
        {7, 8, 9}
    };
    int size = 3; // For a 3x3 matrix

    // Step 2: Initialize sum for both diagonals
    int total_diagonal_sum = 0;

    // Step 3: Iterate to sum elements from both diagonals
    for (int i = 0; i < size; i++) {
        total_diagonal_sum += matrix[i][i];               // Add main diagonal element
        total_diagonal_sum += matrix[i][size - 1 - i];    // Add secondary diagonal element
    }

    // Step 4: Handle overlap for odd-sized matrices
    // If the matrix size is odd, the center element (matrix[size/2][size/2])
    // is counted twice (once for main, once for secondary diagonal).
    // We need to subtract it once to get the correct unique sum.
    if (size % 2 == 1) {
        total_diagonal_sum -= matrix[size / 2][size / 2];
    }

    // Step 5: Print the result
    printf("Matrix:\n");
    for (int i = 0; i < size; i++) {
        for (int j = 0; j < size; j++) {
            printf("%d ", matrix[i][j]);
        }
        printf("\n");
    }
    printf("Sum of both diagonal elements (with overlap handling): %d\n", total_diagonal_sum);

    return 0;
}