Trouble with some functions in Tic-Tac-Toe

[Any1with25c]

#include <iostream>
#include <vector>

using namespace std;

const bool CLEAR_SCREEN = true;
/// @brief Utilizes an escape character sequence to clear the screen

void clearScreen()
{
cout << endl;
if (CLEAR_SCREEN)
{
cout << "\033c";
}
cout << endl;
}

void drawBoard(const vector < char >&board)
{
clearScreen();
for (int i = 0; i < 9; i += 3)
{
cout << " " << board.at(i) << " | " << board.at(i + 1) << " | "
<< board.at(i + 2) << " " << endl;
if (i < 6)
cout << "-----|-----|-----" << endl;
}
cout << endl;
}

void initVector(vector<char> &v)
{
string mapA = "abcdefghijklmnopqrstuvwxyz";
for (int i = 0; i < v.size(); i++)
{
v.at(i) = mapA.at(i);
}
}

int convertPosition(char position)
{
string mapA = "abcdefghijklmnopqrstuvwxyz";
return mapA.find(position);
}

bool validPlacement(const vector <char> &board, int position)
{
if (position > 8 || position < 0 ||
board.at(position) == 'X' || board.at(position) == 'O')
{
return false;
}
else if (position <= 8 || position >= 0)
{
return true;
}
}

bool gameWon(const vector <char> &board)
{
return true;
}

bool boardFull(const vector <char> &board)
{
return true;
}

int getPlay(const vector <char> &board)
{
char play;
cout << "Please choose a position: ";
cin >> play;
cout << endl;
int pos = convertPosition(play);
if (validPlacement(board, pos))
{
return pos;
}
}

const int PLAYER1 = 0;
const int PLAYER2 = 1;

int main()
{
vector <char> board(9);
int curPlay;
int turn = PLAYER1;
initVector(board);
drawBoard(board);
getPlay(board);
return 0;
}

Above is my code for a tic tac toe game with 2 players. I can't seem to get a handle on these problems with these functions:

1) validPlacement: What if both players use the same letter 'o' or 'x'? I need it to make validPlacement false.

2) gameWon: What if the board is only partially filled or there is no row for a winner? I need it to be false.

[coder777]

What if both players use the same letter 'o' or 'x'?

It doesn't matter within this function. You just ckeck whether a placement could be done or not. The player doesn't even have the choice what symbol he want. You don't make a placement.

What if the board is only partially filled or there is no row for a winner?

you need to check whether a symbol is set three times in a row horizontally, vertically, or diagonally

validPlacement() has a potential crash. Better check the position before you use it:

bool validPlacement(const vector <char> &board, int position)
{
if (position > 8 || position < 0)
return false;
else if(board[position] == 'X' || board[position] == 'O') // vector has []
return false;

return true;
}

[Any1with25c]

I've noticed another issue when I compiled it. The board is displayed with its positions. I type in one of them (a - I), and then the game ends.

[coder777]

you need a loop around drawBoard() and getPlay() that goes as long as not gameWon and not boardFull