Question

Write a program that reads in the size of the side of a square and then prints a hollow square of that size out of asterisks and blanks. Your program should work for squares of all side sizes between 1 and \(20 .\) For example, if your program reads a size of \(5,\) it should print

Short answer

Write code that prints '*' for square borders and ' ' for inner spaces.

Step-by-step solution

Understand the Problem

We need to create a program that reads an integer value representing the side length of a square. This program will then print a hollow square using asterisks ('*') and spaces (' ') for squares with side lengths from 1 to 20.

Consider Edge Cases

For a side length of 1, the square will just be a single asterisk. For side lengths 2 and greater, a hollow square is needed, which means the perimeter should contain asterisks while the inner area is filled with spaces.

Plan the Structure of the Program

The program will loop over the rows and columns of the square. For each position, it will determine if an asterisk or a space should be printed based on whether the position is on the edge of the square (top, bottom, or sides).

Write the Code

```python # Read the side length side_length = int(input("Enter the size of the side (between 1 and 20): ")) # Check if the side length is valid if 1 <= side_length <= 20: for row in range(side_length): for col in range(side_length): # Print '*' for the borders, otherwise print a space if row == 0 or row == side_length - 1 or col == 0 or col == side_length - 1: print('*', end='') else: print(' ', end='') print() # Go to the next line after each row else: print("Invalid size. Enter a number between 1 and 20.") ```

Test the Code

Try the code with various input values, such as 1, 5, 10, and 20, to ensure it produces the correct hollow squares. This will help verify the correct structure and boundaries.

Key concepts

Control Flow in Programming

Control flow is a fundamental concept in programming that allows you to dictate the order in which statements are executed. In our task of creating a hollow square, control flow is crucial, as it helps determine when to print an asterisk or a space.
Understanding control flow involves learning about conditional statements and loops. These constructs enable a program to make decisions and perform tasks repeatedly based on certain conditions. In C++, some common control flow statements are `if`, `else`, and various loop structures. In our exercise, we use `if` statements to decide whether a character in the square is part of the border or inside.
Effective control flow ensures that our code is efficient and easy to understand. When designing the program, think about all possible scenarios. Consider edge cases where the input is the smallest or largest possible, which helps in making the program robust.

Loops in C++

Loops are essential when you need to repeat a task multiple times until a condition is met. In C++, loops such as `for`, `while`, and `do-while` are commonly used to iterate over code blocks.
For our hollow square program, we utilize `for` loops to manage row and column iterations of the square. Each row and column coordinate is checked, and based on its position, we either print an asterisk or a space.
Since we are drawing squares, our loops run from `0` to `side_length - 1`. The outer loop handles the rows, and the inner loop handles the columns. This nested loop structure simplifies the process of constructing two-dimensional patterns. Remember, precise structure and termination conditions are key in loops to prevent runtime errors like infinite loops.

Input and Output in C++

Input and output operations are critical for interacting with users in any programming task. In C++, input is generally handled using `cin`, and output is handled using `cout`.
In our hollow square exercise, we first use input commands to read the size of the square's side. It's important to prompt the user clearly, as our program does by asking them to enter a size between 1 and 20. Ensuring input validity is crucial to avoid errors, hence our use of a conditional to check this range.
During output, we print characters (`*` and space) on the console, which gives the visual representation of the hollow square. The `end=''` statement in `cout` ensures that the characters are printed on the same line until a row completes.

Problem Solving in Programming

Problem solving in programming involves breaking down tasks into manageable steps and crafting an efficient code solution. The hollow square program is a classic example of problem-solving, requiring a blend of logical and creative skills.
Begin with a clear understanding of the problem statement. Identify the inputs, processes, and expected outputs. Then, plan your logic thoroughly, as we did, by analyzing each character's position on the square's grid and deciding whether it's part of the outline or interior.
Debugging, testing, and refining are essential components of programming problem solving. Run your program with various test values to ensure that it handles typical, boundary, and edge cases gracefully. Problem solving in programming isn't just about writing code; it's about writing clear, correct, and efficient code, and continually improving it.