Tic Tac Toe C++ Check & Print Winner - c++

Question

have a problem with this coding, how to check and display the winner? I have tried to add it but turns into error due to the function checkWinner().
#include <iostream>
using namespace std;
void showBoard(void);
void playerInput(int p);
void checkWinner();
void nextPlayer(int);
int board[3][3]={{0,0,0},{0,0,0},{0,0,0}};
int main()
{
int r;
int c;
int player;
int winner;
int turns;
cout << "******* Tic Tac Toe Game *******" << endl;
showBoard();
nextPlayer(1);
checkWinner();
return 0;
}
Output board function:
void showBoard(void)
{
int r;
int c;
for(r=0; r<=2; r++)
{
for(c=0; c<=2; c++)
{
if( board [r][c]==0)
cout << "0 ";
else if (board [r][c]==1)
cout << "1 ";
else
cout << "2 ";
}
cout << endl;
}
}
This is the player input function:
void playerInput(int p)
{
int row;
int col;
if(p==1)
cout <<"You are player number 1 \n\n";
else
cout <<"You are player number 2 \n\n";
cout<<"Please enter your coordinate:";
cin>>row;
cout<<"\n";
cin>>col;
if(p==1)
board[--row][--col]=1;
if(p==2)
board[--row][--col]=2;
}
Heres the problem I'm facing now, how to make it display the winner?
void checkWinner()
{
int winner;
for (int i=0; i<=2; i++)
{
if(board[i][0]==board[i][1] && board[i][1]==board[i][2] && board[i][0]!=0)
{
winner=board[i][0];
}
}
for(int i=0; i<=2; i++)
{
if (board[0][i]==board[1][i] && board[1][i]==board[2][i] && board[0][i]!=0)
{
winner=board[0][i];
}
}
if(board[0][0]=board[1][1] && board[1][1]==board[2][2] && board[0][0]!=0)
{
winner=board[0][0];
}
if(board[0][2]=board[1][1] && board[1][1]==board[2][0] && board [0][2]!=0)
{
winner=board[0][2];
}
if(board[0][0]==board[0][1] && board[0][1]==board[0][2]&& board[0][2]==board[0][1]&& board[1][0]==board [1][1]&& board[1][1]==board [1][2]&& board[1][2]==board[2][0]&&board[2][0]==board [2][1]&& board[2][1]==board [2][2] && board [0][0]!=0)
{
winner=0;
}
}
void nextPlayer(int player)
{
playerInput(player);
showBoard();
if(player==1)
player=2;
else
player=1;
nextPlayer(player);
}
The problem is the game is not ended but it still asking for the player to resume and it keep updating the value.
click below to see the problem I'm facing. Thanks!
Click to view my output, it doesn't end the game

Answer 1

Your code has a serious recursion problem. The function checkWinner() in main never gets called because the function nextPlayer(1); is infinitely recursive, since, it lacks a base case.
A recursive base case, is what causes a recursive function to stop its recursion.
Note that in your code:
void nextPlayer(int player)
{
playerInput(player);
showBoard();
if(player==1)
player=2;
else
player=1;
nextPlayer(player);
}
once nextPlayer(1); is called from main, it never returns, because, it always enters into another call of its own nextPlayer(player); at the end of the function. For this you need a base case to stop this recursion at some point from happening.
Now, logically your base case should actually be, checking for a winner before proceeding to play, which is what is handled by the checkWinner() function.
But, the problem is that the checkWinner() function returns void which means nothing so, in its current state, we cannot use it as a base case.
However, if we redesign it to return something such as:
0 for play on
1 or 2 indicating a player has won
and lastly -1 indicating that the board is full and nobody won (a tie).
So, reforming the checkWinner() function as (I also corrected a few conditions so have a close look at the code):
int checkWinner()
{
int winner;
// any of the rows is same
for (int i=0; i<=2; i++)
{
if(board[i][0]==board[i][1] && board[i][1]==board[i][2] && board[i][0]!=0)
{
winner = board[i][0];
return winner;
}
}
// any of the columns is same
for(int i=0; i<=2; i++)
{
if (board[0][i]==board[1][i] && board[1][i]==board[2][i] && board[0][i]!=0)
{
winner = board[0][i];
return winner;
}
}
// 1st diagonal is same
if(board[0][0]==board[1][1] && board[1][1]==board[2][2] && board[0][0]!=0)
{
winner = board[0][0];
return winner;
}
// 2nd diagonal is same
if(board[0][2]==board[1][1] && board[1][1]==board[2][0] && board [0][2]!=0)
{
winner = board[0][2];
return winner;
}
// if we reached here nobody has won yet
// if any empty box on board then play on
for(int i=0; i<=2; i++)
{
for(int j=0; j<=2; j++)
{
if(board[i][j]==0)
{
winner = 0;
return winner;
}
}
}
winner = -1; // all boxes full and nobody won so A tie has occurred
return winner;
}
Now, that it can be used, we will use it in void nextPlayer(int player) function as:
void nextPlayer(int player)
{
int winner = checkWinner();
if( winner == 0) // play on
{
playerInput(player);
showBoard();
if(player==1)
player=2;
else
player=1;
nextPlayer(player);
}
else if(winner == -1)
{
cout<<"\nGame drawn!\n";
}
else
{
cout<<"\nPlayer "<<winner<<" wins!\n"<<endl;
}
}
Note that, the checkWinner() condition is checked before we start to do anything.
And now, the call to checkWinner() in the main function, which was unreachable anyways, is not needed and will now be done before proceeding at every step in void nextPlayer(int player):
#include <iostream>
using namespace std;
void showBoard(void);
void playerInput(int p);
int checkWinner();
void nextPlayer(int);
int board[3][3]={{0,0,0},{0,0,0},{0,0,0}};
int main()
{
int r;
int c;
int player;
int winner;
int turns;
cout << "******* Tic Tac Toe Game *******" << endl;
showBoard();
nextPlayer(1);
return 0;
}
The rest of the functions are correct and will remain the same.

Answer 2

At two points in your code, you have used = in your if statement. This leads to initialization instead of equality checking. You should use == instead of the =.
if (board[0][0] = board[1][1] && /** This should be a == for checking equality */
board[1][1] == board[2][2] &&
board[0][0] != 0)
{
winner=board[0][0];
}
if (board[0][2] = board[1][1] && /** This should be a == for checking equality */
board[1][1] == board[2][0] &&
board[0][2] != 0)
{
winner = board[0][2];
}