Example: Interchange Diagonals of a Matrix in C

// Interchange Diagonals of a Matrix
#include <stdio.h>

#define MAX_SIZE 10 // Define a maximum size for the matrix

int main() {
    int matrix[MAX_SIZE][MAX_SIZE];
    int m, n; // Variables for rows and columns

    // Step 1: Accept matrix dimensions from the user
    printf("Enter the number of rows (M): ");
    scanf("%d", &m);
    printf("Enter the number of columns (N): ");
    scanf("%d", &n);

    // Validate dimensions to ensure they fit within MAX_SIZE
    if (m <= 0 || n <= 0 || m > MAX_SIZE || n > MAX_SIZE) {
        printf("Invalid dimensions. M and N must be positive and less than or equal to %d.\n", MAX_SIZE);
        return 1; // Indicate an error
    }

    // Step 2: Check if the matrix is square (M == N) for diagonal interchange
    if (m != n) {
        printf("Diagonal interchange is typically defined for square matrices (M=N).\n");
        printf("Cannot interchange diagonals for a non-square matrix of order %dx%d.\n", m, n);
        return 1; // Indicate an error or non-applicable scenario
    }

    // Step 3: Accept matrix elements from the user
    printf("Enter matrix elements:\n");
    for (int i = 0; i < m; i++) {
        for (int j = 0; j < n; j++) {
            printf("Enter element [%d][%d]: ", i, j);
            scanf("%d", &matrix[i][j]);
        }
    }

    // Step 4: Display the original matrix
    printf("\nOriginal Matrix:\n");
    for (int i = 0; i < m; i++) {
        for (int j = 0; j < n; j++) {
            printf("%d\t", matrix[i][j]);
        }
        printf("\n");
    }

    // Step 5: Interchange the main and secondary diagonals
    // The main diagonal elements are at matrix[i][i]
    // The secondary diagonal elements are at matrix[i][m - 1 - i]
    for (int i = 0; i < m; i++) {
        int temp = matrix[i][i]; // Store main diagonal element
        matrix[i][i] = matrix[i][m - 1 - i]; // Replace with secondary diagonal element
        matrix[i][m - 1 - i] = temp; // Place stored main diagonal element into secondary position
    }

    // Step 6: Display the matrix after diagonal interchange
    printf("\nMatrix after interchanging diagonals:\n");
    for (int i = 0; i < m; i++) {
        for (int j = 0; j < n; j++) {
            printf("%d\t", matrix[i][j]);
        }
        printf("\n");
    }

    return 0; // Indicate successful execution
}