ETH_Informatik/Informatik_I/Exercise_7/Task_3

Task 3: [Hidden tests] Trapezoid printing

• Task
  • Examples
    • Rightsideup trapezoid with height and width \(3\) (aka a triangle)
    • Rightsideup trapezoid with base width 5 and height 2
  • Subtask 1: print_trapezoid
  • Subtask 2: print_diamond:
  • Subtask 3: print_hourglass:
• Hidden test cases
  • Persistent input
• Solution

Task

In this exercise, you are going to print trapezoids. A trapezoid is defined by the width of its base and its height. A trapezoid can also either be rightsideup or upsidedown.

Note: It is mandatory to use recursive implementation for this task.

Examples

Rightsideup trapezoid with height and width \(3\) (aka a triangle)

  0
 0 0
0 0 0

Upsidedown trapezoid with height and width \(3\) (aka an upsidedown triangle)

0 0 0
 0 0
  0

Rightsideup trapezoid with base width 5 and height 2

 0 0 0 0
0 0 0 0 0

Subtask 1: print_trapezoid

Implement the function print_trapezoid. The function takes three arguments:

• int base_width: The width of the trapezoid's base
• int height: The height of the trapezoid
• int offset_left: The number of spaces between the left edge of the trapezoid's base and the left edge of the console.
• bool upsidedown: Boolean indicating whether or not the trapezoid is upsidedown or rightsideup.

When called, the function should print the specified trapezoid to the console.

Subtask 2: print_diamond:

Implement the function print_diamond.

The function prints a diamond with a given center width to the console. A diamond is a rightsideup trapezoid on top of an upsidedown trapezoid.

For example, a diamond of width \(5\) looks as follows:

    0
   0 0
  0 0 0
 0 0 0 0
0 0 0 0 0
 0 0 0 0
  0 0 0
   0 0
    0

Subtask 3: print_hourglass:

Implement the function print_hourglass.

The function prints an hourglass with a given base width to the console. A hourglass is an upsidedown trapezoid on top of a rightsideup trapezoid.

For example, an hourglass of width \(5\) looks as follows:

0 0 0 0 0
 0 0 0 0
  0 0 0
   0 0
    0
   0 0
  0 0 0
 0 0 0 0
0 0 0 0 0

Note: The autograder will only accept output that exactly matches the expected result. Therefore, do not output anything with std::cout beyond what is strictly required (i.e., ” ","0", and std::endl /"n=“). For debugging messages, use =std::cerr as in:

std::cerr << "This is a test message." << std::endl;

Those will be ignored by the autograder.

Hidden test cases

This exercise has some hidden test cases. You will see whether these tests passed or failed, but you will not see the test input or the expected output.

Persistent input

To help you in testing your code, you can enter your custom test input in input.txt. When running the program, you can let CodeExpert read the input from the file.

Write some program input in input.txt. Run the program as usual. Type f (no spaces) in the terminal window and press Enter. The program will use the contents of input.txt as input. Using this feature is entirely optional and does not affect your score.

Solution

#include <assert.h>

#include <iostream>

#include "solution.h"

void print_row(int n_bricks, int offset_left) {
  // print spaces for offset
  for (int i = 0; i < offset_left; ++i) {
    std::cout << " ";
  }

  // print bricks
  for (int i = 0; i < n_bricks; ++i) {
    if (i != 0) {
      std::cout << " ";
    }
    std::cout << "0";
  }
  std::cout << std::endl;
}

void print_trapezoid(int base_width, int height, int offset_left,
                     bool upsidedown) {
  assert(base_width >= height);

  if (upsidedown == true) {
    if (height == 0)
    return;

    print_row(base_width, offset_left);
    print_trapezoid(base_width - 1, height - 1, offset_left + 1, upsidedown);
  } else if (upsidedown == false) {
    if (height == 0)
    return;

    print_row(base_width - height + 1, offset_left + height - 1);
    print_trapezoid(base_width, height - 1, offset_left, upsidedown);
}
}

void print_diamond(int center_width) {
  print_trapezoid(center_width, center_width, 0, false);
  print_trapezoid(center_width - 1, center_width - 1, 0, true);
}

void print_hourglass(int base_width) {
  print_trapezoid(base_width, base_width, 0, true);
  print_trapezoid(base_width, base_width - 1, 0, false);

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