Connect Four game...need help

I am making a connect four game in console mode.
I have just written the function that determines what to do when the current player drops their piece in a row.

Here's what it is:

Code:

---

void DropRow(int row)
{
  char piece;

  if (p1.myturn)
      piece = 'Q';
  else if (p2.myturn)
      piece = 'X';
  //check drop and win criteria
  //not done yet
  //Big stuff--------------
  if (putvert < 0)
  {
      msg = 1;
      putvert = 7;
      StartGame();
  }

  if (board[putvert][row-1] != 'O')
  {
      putvert--;
      DropRow(row);
  }

  if (board[putvert][row-1] == 'O')
  {
      board[putvert][row-1] = piece;
  }

  //End of big stuff-------
  SwitchTurns();
  putvert = 7;
}

---

Putvert is an int that determines where to place the piece vertically. Board[][] is the char that stores all the grid spots. There is a global struct named Player that stores 2 people's score, name, and turn status.

'O' is an empty grid space, 'Q' is player one's piece, and 'X' is player two's piece. The 'msg' you see being assigned to 1 is an instruction to a function that prints error messages. StartGame() is the main game loop, where it prints all the necessary stuff, the board, and lets they player input their row choice.

Now here is the bug. If a player drops a piece on top of a piece that exists, they get an extra turn. I have no idea why it is happening.

Here is the switch turn function:

Code:

---

void SwitchTurns()
{
  if (p1.myturn == TRUE)
  {
      p1.myturn = FALSE;
      p2.myturn = TRUE;
  }
  else if (p2.myturn == TRUE)
  {
      p1.myturn = TRUE;
      p2.myturn = FALSE;
  }
}

---

Anyone have any ideas?

Is an 'else if' checked even if the first 'if' is correct? (I have no idea, and no way to test that quickly right now); where for art thou Prelude, Barjor?

If it is, it would change it to player 2's turn, then back to player 1's I guess.

There is no need for the second if check. There can only be one of two things: It's playerA's turn, or it's playerB's turn. There is no other possibility. Therefore, there is no need for the second check.

Code:

---

void SwitchTurns()
{
  if (p1.myturn == TRUE)
  {
      p1.myturn = FALSE;
      p2.myturn = TRUE;
  }
  else
  {
      p1.myturn = TRUE;
      p2.myturn = FALSE;
  }
}

---

However, I doubt this is where your problem lies. The real problem is likely where you check to see who's turn it is.

Code:

---

void DropRow(int row)
{
  char piece;

    /**
    *** No need for second 'if'.
    **/
    piece = p1.myturn ? 'Q' : 'X';

  //check drop and win criteria
  //not done yet
  //Big stuff--------------
  if (putvert < 0)
  {
      msg = 1;
      putvert = 7;
      StartGame();
  }

  if (board[putvert][row-1] != 'O')
  {
      putvert--;
      DropRow(row);
  }

    /**
    *** You never check 'row' for
    *** validity. This could be your
    *** problem.
    **/
  if (board[putvert][row-1] == 'O')
  {
      board[putvert][row-1] = piece;
  }

---

Personally, I wouldn't have the drop function handle my side switching. I'd basicly do something like:

Code:

---

while( !game_over )
{
    ShowBoard( );
    row = PromptRow( p1.myturn ? p1 : p2 );
    Drop( row );
    game_over = CheckWin( );
    SwitchTurns( );
}
CongradulateWinner( );

---

Quzah.