Tower of Hanoi Case Study

towerOfHanoi.cpp

/*
  Author: gazmull <vescalaw@gmail.com>
  Description: [Case Study] Tower of Hanoi with data structuring.
*/

#include <iostream>
#include <iomanip>

using namespace std;

int
    inputSize
  , moves
  , * towers
  , * towerSizes;

// Towers-related functions
void
    printTowers()
  , modifyTowers(int towerA, int towerB);

// I/O streaming functions
void pausePrint(string message = "\n");

// Tower functions
namespace Tower {
  int index(int x, int y) { return (x * inputSize) + y; };
  int size(int tower) { return towerSizes[tower]; };
  int top(int tower) { return -1 * (size(tower) - inputSize); };
  int topValue(int tower) { return towers[index(tower, top(tower))]; };
};

// Initialiser
int main() {
  cout << "Number of towers: ";
  cin >> inputSize;

  if (inputSize < 3)
    return main();

  // Use 1D Array for storing tower numbers, with their respective tower size in another array
  // Please refer to Tower::index for indexing
  moves = 0;
  towers = new int[inputSize * inputSize];
  towerSizes = new int[inputSize];

  // Print vertically
  for (int i = 0; i < inputSize; i++)
    for (int j = 0; j < inputSize; j++)
      if (!i) {
        towers[Tower::index(0, j)] = j + 1;
        towerSizes[i] = inputSize;
      }
      else {
        towers[Tower::index(i, j)] = 0;
        towerSizes[i] = 0;
      }

  printTowers();

  return 0;
}

// Display/Update towers sheet
void printTowers() {
  system("cls");

  cout
    << "Moves occurred: " << moves
    << "\nGame Rules:"
    << "\n  * Only 1 number per move"
    << "\n  * You cannot stack larger number with a smaller number"
    << "\n  * You cannot win with getting all numbers back to tower 1 after scrambling them."
    << "\n\n";

  for (int i = 1; i <= inputSize; i++)
    cout << setw(5) << i;

  cout << "\n\n";

  for (int i = 0; i < inputSize; i++) {
    for (int j = 0; j < inputSize; j++)
      cout << setw(5) << towers[Tower::index(j, i)];

    cout << endl;
  }
  
  int
      towerA
    , towerB;

  // Ask for input with space character as separator
  cout
    << endl
    << "[MOVE FROM] [MOVE TO]: ";
  cin >> towerA >> towerB;
  
  modifyTowers(towerA - 1, towerB - 1);
}

/*
  Towers checker
    - Malicious act checks
    - Transferring of number between towers
    - Check win condition
*/
void modifyTowers(int towerA, int towerB) {
  // Malicious act checks
  if (towerA == towerB) {
    pausePrint("Wrong move. You cannot select the same tower.");

    return printTowers();
  } else if (!Tower::topValue(towerA)) {
    pausePrint("Wrong move. You cannot move anything from an empty tower.");

    return printTowers();
  } else if (Tower::topValue(towerB) && Tower::topValue(towerA) > Tower::topValue(towerB)) {
    pausePrint("Wrong move. Please move to an empty tower or a tower with higher top number.");

    return printTowers();
  }

  /*
    Transferring of number between towers
      - For some reason, removing `- 1` and/or adding `-1` at `Tower::top` breaks these re-assignments.
        I have yet to know why...
      - Update tower sizes
      - Track moves
  */
  towers[Tower::index(towerB, Tower::top(towerB) - 1)] = Tower::topValue(towerA);
  towers[Tower::index(towerA, Tower::top(towerA))] = 0;

  towerSizes[towerA]--;
  towerSizes[towerB]++;

  moves++;

  // Check win condition
  if (Tower::size(towerB) == inputSize && towerB) {
    cout << "You win. Moves occurred: " << moves;
    pausePrint();

    tryAgain:
      char answer;
      cout << "Try again? (y/n): ";
      cin >> answer;

    switch (answer) {
      case 'y':
        // Free memory && call main function
        delete[] towers;
        delete[] towerSizes;
        system("cls");

        main();
      break;

      case 'n':
        exit(0);
      break;

      default: goto tryAgain;
    }
  }

  printTowers();
}

void pausePrint(string message) {
  cout << message << endl;

  system("pause");
}