TicTacToe

#include <iostream>

using namespace std;

#define PLY_ONE 1
#define PLY_TWO 2
#define NO_PLY 0

int field[3*3];

int sign(int val)
{
    if(val>0)
    {
    return 1;
    }
    else
    {
    return 0;
    }
}

void clearField()
{
    for(int i=0; i<9;i++)
    {
        field[i] = NO_PLY;
    }
}

void print_field()
{
    for(int y=0;y<3;y++)
    {
        for(int x=0;x<3;x++)
        {
            switch (field[x + y*3])
            {
                case NO_PLY:
                    cout <<" ";
                break;
                case PLY_ONE:
                    cout <<"X";
                break;
                case PLY_TWO:
                    cout <<"O";
                break;
            }

            if(x!=2)
            {
                cout <<" | ";
            }
        }
        cout <<"\n";
    }
}

int check_field()
{
    int sum = 0;
    int sum2 = 0;
    sum = field[0]+field[1]+field[2];
    sum2 = sign(field[0])+sign(field[1])+sign(field[2]);
    if((sum==3 || sum==6) && sum2==3)
    {
        return field[0];
    }

    sum = field[3]+field[4]+field[5];
    sum2 = sign(field[3])+sign(field[4])+sign(field[5]);
    if((sum==3 || sum==6) && sum2==3)
    {
        return field[3];
    }

    sum = field[6]+field[7]+field[8];
    sum2 = sign(field[6])+sign(field[7])+sign(field[8]);
    if((sum==3 || sum==6) && sum2==3)
    {
        return field[6];
    }

    sum = field[0]+field[3]+field[6];
    sum2 = sign(field[0])+sign(field[3])+sign(field[6]);
    if((sum==3 || sum==6) && sum2==3)
    {
        return field[3];
    }

    sum = field[1]+field[4]+field[7];
    sum2 = sign(field[1])+sign(field[4])+sign(field[7]);
    if((sum==3 || sum==6) && sum2==3)
    {
        return field[1];
    }

    sum = field[2]+field[5]+field[8];
    sum2 = sign(field[2])+sign(field[5])+sign(field[8]);
    if((sum==3 || sum==6) && sum2==3)
    {
        return field[2];
    }

    sum = field[0]+field[4]+field[8];
    sum2 = sign(field[0])+sign(field[4])+sign(field[8]);
    if((sum==3 || sum==6) && sum2==3)
    {
        return field[0];
    }

    sum = field[2]+field[4]+field[6];
    sum2 = sign(field[2])+sign(field[4])+sign(field[6]);
    if((sum==3 || sum==6) && sum2==3)
    {
        return field[2];
    }

    return NO_PLY;
}

int main(int argc, char *argv[])
{
    int turn = PLY_ONE;
    bool playing = true;
    int chosen_field = 1;
    bool valid_field=false;

    clearField();

    cout <<"Wilkommen im Kommandozeilen TicTacToe!\n";
    cout <<"Das Spielfeld:\n\t1 | 2 | 3\n\t4 | 5 | 6\n\t7 | 8 | 9\n";
    cout <<"Zeichen von Spieler 1: X\nZeichen von Spieler 2: O\n\n";

    while(playing)
    {
        if(turn==NO_PLY)
            turn=PLY_ONE;


        cout <<"Spieler "<<turn<<" ist am Zug.\n";

        valid_field = false;

        while(!valid_field)
        {
            cout <<"Feld: ";
            cin >> chosen_field;
            if(chosen_field<1 || chosen_field>9)
            {
                cout <<"Feld "<<chosen_field<<" exisitiert nicht!\n\n";
                continue;
            }

            chosen_field--;
            if(field[chosen_field]!=NO_PLY)
            {
                cout <<"Feld "<<chosen_field+1<<" ist schon belegt!\n\n";
                continue;
            }
            field[chosen_field] = turn;
            valid_field = true;
            cout <<"\n";
        }

        if(turn==PLY_ONE)
        {
            turn=PLY_TWO;
        }
        else
        {
            turn=PLY_ONE;
        }

        print_field();

        int winningPlayer = NO_PLY;
        winningPlayer = check_field();
        if(winningPlayer!=NO_PLY)
        {
            cout <<"Spieler "<<winningPlayer<<" hat gewonnen!";
            playing = false;
        }

    }

    return 0;
}