main.cpp

#include <iostream>
#include <stdlib.h>
#include <time.h>

using namespace std;

char field[10];

void singleplayer();
void multiplayer();
void help();
bool checkFull();
bool checkWin(char);
char keyInput(bool x);
void AI(int);


void clearConsole()
{
    system("clear");
}

void resetField()
{
    for(int i = 0; i < 10; i++)
    {
	field[i] = ' ';
    }
}

void menu()
{
    while(true)
    {
	resetField();
	char inputmenu;
	cout << "\n\n"
	     << "MENU\n\n"
	     << "1: Singleplayer\n"
	     << "2: Multiplayer\n"
	     << "3: Help\n"
	     << "4: Quit\n\n\n"
	     << "Input: ";
	cin >> inputmenu;
	
	if(inputmenu == '1')singleplayer();
	else if(inputmenu == '2')multiplayer();
	else if(inputmenu == '3')help();
	else if(inputmenu == '4' || inputmenu == 'q')return;
	else {clearConsole(); cout << "\nInvalid Input!";}
    }
}

void drawField()
{
    clearConsole();
    cout << "\n\n\n"
	 << "     " << field[1] << " | " << field[2] << " | " << field[3] << endl
	 << "    ---|---|---" << endl
	 << "     " << field[4] << " | " << field[5] << " | " << field[6] << endl
	 << "    ---|---|---" << endl
	 << "     " << field[7] << " | " << field[8] << " | " << field[9] << endl;
}

void singleplayer()
{
    clearConsole();
    char input = ' ';
    int difficulty = 0;
    cout << "\n\n\nDIFFICULTY\n\n\n1: Easy\n\n2: Medium\n\n3: Hard\n\n";
    cout << "\n\n\nInput: ";
    cin >> input;
    switch(input)
    {
	case '1': difficulty = 1; break;
	case '2': difficulty = 2; break;
	case '3': difficulty = 3; break;
	case 'q': return; break;
	default:	cout << "\nInvalid Input!"; singleplayer(); break;
    }
    
    while(true)
    {
	drawField();
	if(checkWin('O'))
	{
	    cout << "\nComputer has won\n\n";
	    return;
	}
	if(checkFull())
	{
	    cout << "\nTie\n\n";
	    return;
	}
	input = keyInput(true);
	drawField();
	if(input == 'q')
	{
	    return;
	}
	if(checkWin('X'))
	{
	    cout << "\nPlayer has won\n\n";
	    return;
	}
	AI(difficulty);
    }
}

void multiplayer()
{
    char input = ' ';
    bool player1Turn = true;
    while(true)
    {
	drawField();
	if(checkWin('X'))
	{
	    cout << "\nPlayer1 has won\n\n";
	    return;
	}
	else if(checkWin('O'))
	{
	    cout << "\n Player2 has won\n\n";
	    return;
	}
	if(checkFull())
	{
	    cout << "Tie\n\n";
	}
	input = keyInput(player1Turn);
	if (input == 'q')
	{
	    return;
	}
	player1Turn = !player1Turn;
    }
}

void help()
{
    clearConsole();
    cout << "\n\n\nHELP\n\nSingleplayer:\nIn Singleplayermode you play against the Computer\n\nMultiplayer:\nIn Multiplayermode you play against a second player. Input switches between X and O. You can also play this mode if you want to test new tactics or just want to play against yourself.\n\nControls:\nTo choose a field you must enter a number between 1 and 9. The first field is in the top left. the second right next to it etc.\n\n";
    return;
}

char keyInput(bool x)
{
    while(true)
    {
	cout << "\n\nInput: ";
	char input = ' ';
	cin >> input;
	int inputNumber = input - '0';
	if(inputNumber > 9 || inputNumber < 1)
	{
	    if(input == 'q')
		return input;
	    else
		cout << "\nInvalid Input!";
	}
	else if(field[inputNumber] != ' ')
	{
	    cout << "\nThis field is already used";
	}
	else
	{
	    if(x)
		field[inputNumber] = 'X';
	    else
		field[inputNumber] = 'O';
	    return input;
	}
    }
}

bool checkWin(char sign)
{
    if (field[1] == sign && field[2] == sign && field[3] == sign || field[1] == sign && field[4] == sign && field[7] == sign || field[1] == sign && field[5] == sign && field[9] == sign || field[2] == sign && field[5] == sign && field[8] == sign || field[3] == sign && field[6] == sign && field[9] == sign || field[3] == sign && field[5] == sign && field[7] == sign || field[4] == sign && field[5] == sign && field[6] == sign || field[7] == sign && field[8] == sign && field[9] == sign)
    {
	return true;
    }
    return false;
}

bool checkFull()
{
    for(int i = 1; i <= 9; i++)
    {
	if(field[i] == ' ')
	{
	    return false;
	}
    }
    return true;
}

void AI(int difficulty)
{
    if(checkFull())
    {
	return;
    }
    
    srand(time(nullptr));
    
    if(difficulty == 1)
    {
	int check = rand() % 3;
	if(check != 1)
	{
	    for(int i = 1; i < 10; i++)
	    {
		if(field[i] == ' ')
		{
		    field[i] = 'O';
		    if(checkWin('O'))
		    {
			return;
		    }
		    else
		    {
			field[i] = ' ';
		    }
		}
	    }
	}
	else if(check != 2)
	{
	    for(int i = 1; i < 10; i++)
	    {
		if(field[i] == ' ')
		{
		    field[i] = 'X';
		    if(checkWin('X'))
		    {
			field[i] = 'O';
			return;
		    }
		    else
		    {
			field[i] = ' ';
		    }
		}
	    }
	}
	while (true)
	{
	    int i = rand() % 9 + 1;
	    if (field[i] == ' ')
	    {
		field[i] = 'O';
		return;
	    }
	}
    }
    else if(difficulty == 2)
    {
	int check = rand() % 5 + 1;
	if(check != 3)
	{
	    for(int i = 1; i < 10; i++)
	    {
		if(field[i] == ' ')
		{
		    field[i] = 'O';
		    if(checkWin('O'))
		    {
			return;
		    }
		    else
		    {
			field[i] = ' ';
		    }
		}
	    }
	}
	else if(check != 4)
	{
	    for(int i = 1; i < 10; i++)
	    {
		if(field[i] == ' ')
		{
		    field[i] = 'X';
		    if(checkWin('X'))
		    {
			field[i] = 'O';
			return;
		    }
		    else
		    {
			field[i] = ' ';
		    }
		}
	    }
	}
	while (true)
	{
	    int i = rand() % 9 + 1;
	    if (field[i] == ' ')
	    {
		field[i] = 'O';
		return;
	    }
	}
    }
    else if(difficulty == 3)
    {
	//Hard
	//Check if AI can win
	for(int i = 1; i < 10; i++)
	{
	    if(field[i] == ' ')
	    {
		field[i] = 'O';
		if(checkWin('O'))
		{
		    return;
		}
		else
		{
		    field[i] = ' ';
		}
	    }
	}
	
	//Check if Player can win and stop it ;)
	for(int i = 1; i < 10; i++)
	{
	    if(field[i] == ' ')
	    {
		field[i] = 'X';
		if(checkWin('X'))
		{
		    field[i] = 'O';
		    return;
		}
		else
		{
		    field[i] = ' ';
		}
	    }
	}
	
	//Set to field in the middle with a chance when it is still free
	int middle = rand() % 4;
	if(field[5] == ' ' && middle != 1)
	{
	    field[5] = 'O';
	    return;
	}
	
	//Select random field
	while(true)
	{
	    srand(time(nullptr));
	    int i = rand() % 9 + 1;
	    if(field[i] == ' ')
	    {
		field[i] = 'O';
		return;
	    }
	}
    }
    else
    {
	return;
    }
}

int main() {
    srand(time(nullptr));
    menu();
  
    return 0;
}