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Tic-Tac-Toe - Detecting a "tie" error

HellfireXP (143)
Everything seems to be working fine unless the game ends in a tie (all tic-tac-toe squares are filled and no one has won the game). Can someone take a look at my code and see if you can identify the problem I am missing. The error is a logic one - not compile error, and is most likely with the code in the very last function at the bottom. :/

(If you enter 4, 0,1,2,3,5,6,7,8 you will quickly reach a tie game)

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#include <iostream>
#include <vector>
#include <string>
using namespace std;

//Global Variable
vector<string> contents (9);

//Declare Functions
void DisplayGrid();
string CheckEnd();
void NextPlayer(string&);

int main()
{
	//Main Scope Variables
	bool gameRunning = true;
	string thisPlayer = "X";
	int gridCode;
	bool validMove = false;

	//Clear board contents
	for (int i=0; i < contents.size(); ++i)
		contents[i] = " ";
	
	//Show the grid
	DisplayGrid();
	
	//Run game loop
	do {	
		//Get a valid response from user
		while (validMove == false)
		{
			cout << "\nEnter a valid grid code to place " << thisPlayer << ": ";
			cin >> gridCode;
			if (cin.fail()) return 0;
			if (gridCode <= 8 && gridCode >= 0)
				if (contents[gridCode] == " ") validMove = true;
		}

		//Set the contents of the grid square to player response
		contents[gridCode] = thisPlayer;

		//Show the updated grid
		DisplayGrid();

		//Check for a win
		string aWin = CheckEnd();
		if (aWin != "")
		{
			//GAME OVER!
			if (aWin != "c") cout << "Player " << aWin << " has won the game!\n\n";
			if (aWin == "c") cout << "Awww.. nobody won this round.\n\n";
			gameRunning = false;
		}

		//Toggle next player's turn
		NextPlayer(thisPlayer);

		//Reset for next loop iteration
		validMove = false;

	} while (gameRunning);

	cout << "\n\n\n";
	system("pause");
	return 0;
}

void NextPlayer(string &thisplyr) { thisplyr = (thisplyr == "X") ? "O" : "X"; }


void DisplayGrid()
{
	system("CLS");
	cout << "GRID CODES: \n";
	cout << " " << 0 << " | " << 1 << " | " << 2 << "\n";
	cout << "-----------\n";
	cout << " " << 3 << " | " << 4 << " | " << 5 << "\n";
	cout << "-----------\n";
	cout << " " << 6 << " | " << 7 << " | " << 8 << "\n";
	cout << "\n\n";
	cout << " " << contents[0] << " | " << contents[1] << " | " << contents[2] << "\n";
	cout << "-----------\n";
	cout << " " << contents[3] << " | " << contents[4] << " | " << contents[5] << "\n";
	cout << "-----------\n";
	cout << " " << contents[6] << " | " << contents[7] << " | " << contents[8] << "\n";
}

string CheckEnd()
{
	string w = "";
	//Check for a winning combination
	if (contents[0] != " " && contents[0] == contents[1] && contents[1] == contents[2]) w = contents[0];
	if (contents[3] != " " && contents[3] == contents[4] && contents[4] == contents[5]) w = contents[3];
	if (contents[6] != " " && contents[6] == contents[7] && contents[7] == contents[8]) w = contents[6];
	if (contents[0] != " " && contents[0] == contents[3] && contents[3] == contents[6]) w = contents[0];
	if (contents[1] != " " && contents[1] == contents[4] && contents[4] == contents[7]) w = contents[1];
	if (contents[2] != " " && contents[2] == contents[5] && contents[5] == contents[8]) w = contents[2];
	if (contents[0] != " " && contents[0] == contents[4] && contents[4] == contents[8]) w = contents[0];
	if (contents[2] != " " && contents[2] == contents[4] && contents[4] == contents[6]) w = contents[2];

	//If no win, check to see if game ended in tie
	bool NOTtied = false;
	if (w == "")
	{
	  for (int i =0; i<contents.size(); ++i)
		  if (contents[i] == " ") NOTtied = true;

	  if (NOTtied = false) w = "c";
	}
	return w;
}
Hippogriff (727)
Check your if statement on line 110

(Hint: =, ==)
HellfireXP (143)
DOH... What a noob mistake. :p Got it fixed, thanks! :D
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