Example: Hollow Diamond Inscribed in a Rectangle in C++

// Hollow Diamond Inscribed in a Rectangle
#include <iostream> // Required for input/output operations (cin, cout)
#include <cmath>    // Required for the abs() function

int main() {
    // Step 1: Get the size from the user
    // The input 'n' determines the 'radius' of the diamond and
    // thus the overall dimensions of the square grid (2*n - 1 by 2*n - 1).
    int n;
    std::cout << "Enter the size for the diamond (e.g., 3 for a 5x5 grid): ";
    std::cin >> n;

    // Calculate total dimensions based on 'n'
    // A diamond with 'n' as its half-width/height will have
    // (2*n - 1) rows and (2*n - 1) columns.
    int total_rows = 2 * n - 1;
    int total_cols = 2 * n - 1;
    
    // The center row/column index of the grid
    int center_coord = n - 1;

    // Step 2: Iterate through each row and column of the grid
    for (int row = 0; row < total_rows; ++row) {
        for (int col = 0; col < total_cols; ++col) {
            // Step 3: Check conditions for printing '*' or ' '

            // Condition for the rectangle border
            // An asterisk is printed if the cell is on the top, bottom, left, or right edge.
            bool is_rectangle_border = (row == 0 || row == total_rows - 1 ||
                                        col == 0 || col == total_cols - 1);

            // Condition for the hollow diamond perimeter
            // A point (row, col) is on the perimeter of a diamond centered at (center_coord, center_coord)
            // with a 'radius' of center_coord if the sum of absolute differences
            // from the center equals the 'radius'.
            bool is_diamond_perimeter = (std::abs(row - center_coord) + std::abs(col - center_coord) == center_coord);

            // Step 4: Print '*' if either condition is met, otherwise print ' '
            if (is_rectangle_border || is_diamond_perimeter) {
                std::cout << "*";
            } else {
                std::cout << " ";
            }
        }
        // Move to the next line after each row is complete
        std::cout << std::endl;
    }

    return 0;
}