Problems with variable initilization

[warburp]

Hello When i compile the following program it runs but when there is input for Player one the compiler stops and says variable b is being used without being initialized and can figure out why

#include <iostream>

using namespace std;

char square[3][3] = {'1', '2', '3', '4', '5' ,'6', '7', '8', '9'};
bool CheckWin(int a, int b);
void Board();
int Turn;
int move(int Turn, char Player);

int main()
{	
	int Turn;
	int Valid = 0;
	bool gamewon = false;
	int charsplaced = 0;
	char Player = 'O';
	int a;
	int b;



	Board();
	cout << "Above is how the various moves are identified" << endl;
	system("pause");

	for(int a = 0; a <= 3; a++)
	{
		for(int b = 0; b <= 3; b++)
			square[a][b] = ' ';
	}
	Board();
	while(!gamewon)
	{
		if (Valid != -1)
		{
			if(Player == 'O')
			{
				cout << "Your' move" << endl;
				Player = 'X';
			}
			else
			{
				cout << "TEST";
				Player = 'O';
			}
		}
		while(true)
		{
			if(charsplaced == 9)
			{
				break;
			}
			cin >> Turn;
			if(Turn <=9 && Turn >=1)
			{
				break;
			}
			else
			{
				cout << "\nPlease enter a value between 1 and 9: ";
				if(cin.fail())
				{
					cin.clear();
					char c;
					cin >> c;
				}
			}
		}
		if(charsplaced == 9)
		{
			break;
		}
		Valid = move(Turn, Player); 
			if(Valid == -1)
				cout << "That is an invalid move try again";
			else
			{
				gamewon = CheckWin(a, b);
				charsplaced ++;
				system("cls");
				Board();
			}
			}
	system("cls");
	if(charsplaced == 9)
	{
		cout << "Draw\n";
		system("pause");
		return 0;
	}
	if (Player == 'X')
	{
		cout << "You win";
	}
	else
	{
		cout << "I win";
	}
	system("pause");
	return 0;
}

int move(int Turn, char Player)
{
	if (Turn >=0 && Turn <= 9)
	{
		int a;
		int b;
		for (a = 0, b = 0; ((a*3)+(b+1)) != Turn; a++, b++)
			if(square[a][b] == ' ')
			{
			square[a][b] = Player;
			return a, b;
			}
			else
			{
				return -1;
			}
	}
}
bool CheckWin(int a, int b)
{
	int vertical = 1;
	int horizontal = 1;
	int diagonal1 = 1;
	int diagonal2 = 1;
	char Player = square[a][b];
	int i;
	int ii;


	for(i = a + 1; square[i][b] == Player && i <= 4; i++, vertical++);
	for(i = a - 1; square[i][b] == Player && i >= 0; i--, vertical++);
		if(vertical >= 3)
			return true;
	for(i = b - 1; square[a][i] == Player && i >= 0; i--, horizontal++);
	for(i = b + 1; square[a][i] == Player && i <= 4; i++, horizontal++);
		if(vertical >= 3)
			return true;
	for(i = a - 1, ii = b - 1; square[i][ii] == Player && i >= 0 && ii >=0; i--, ii--, diagonal1++);
	for(i = a + 1, ii = b + 1; square[i][ii] == Player && i <= 4 && ii <=4; i++, ii++, diagonal1++);
		if(diagonal1 >= 3)
			return true;
	for(i = a - 1, ii = b + 1; square[i][ii] == Player && i >= 0 && ii <=4; i--, ii++, diagonal2++);
	for(i = a + 1, ii = b - 1; square[i][ii] == Player && i <= 4 && ii <=0; i++, ii--, diagonal2++);
		if(diagonal2 >= 3)
			return true;
	return false;
}

void Board()
{
	system("cls");
	cout << "Player 1 (X) - Computer (O)" << endl << endl;
	cout << endl;

	cout << "     |     |     " << endl;
	cout << "  " << square[0][0] << "  |  " << square[0][1] << "  |  " << square[0][2] << endl;

	cout << "_____|_____|_____" << endl;
	cout << "     |     |     " << endl;
	
	cout << "  " << square[1][0] << "  |  " << square[1][1] << "  |  " << square[1][2] << endl;

	cout << "_____|_____|_____" << endl;
	cout << "     |     |     " << endl;

	cout << "  " << square[1][0] << "  |  " << square[2][1] << "  |  " << square[2][2] << endl;

	cout << "     |     |     " << endl << endl;
}

[Chervil]

Lines 18 and 19, variables a and b are defined, but not initialised with any particular value.

Then at line 70, function CheckWin(a, b) is called.

Are either a or b ever given any value before that function call?

[warburp]

they are within function move(int Turn, char Player) and those are the values id like to use

[freddy92]

Your call to CheckWin on line 79 uses a and b, but in the current scope they have never been initialized. You declare them, but then for your for loops you actually declare NEW variables also named a and b, which go out of scope once the for loops end. So you're left with a and b variables that have garbage values. Set them to something before your call and you'll be fine.

[K0T4K0t4]

the reason your getting the segmentation fault is from line 79
gamewon = CheckWin(a, b);

in the begining you do

int a;
	int b;



	Board();
	cout << "Above is how the various moves are identified" << endl;
	system("pause");

	for(int a = 0; a <= 3; a++)
	{
		for(int b = 0; b <= 3; b++)
			square[a][b] = ' ';
	}

redeclaring int a =0 and int b = 0 in the for loop shadows your original declarations so when the program reaches line 79 the is nothing in a and b. your for loops should be

	for(a = 0; a <= 3; a++)
	{
		for(b = 0; b <= 3; b++)
			square[a][b] = ' ';
	}

[Chervil]

Function move() has local variables called a and b. Those are unrelated to the variables a and b in function main().

[warburp]

ok i thank you all for the help i see whats wrong now but now im unsure how i would get the value i get for a and b in function move() out to the function CheckWin()

[Chervil]

Instead of defining new variables in function move(), you could pass by reference the variables from main().

http://www.cplusplus.com/doc/tutorial/functions2/

[warburp]

Thank you i got past that variable now i need to figure out why the move function isn't moving where i want but that's just a math error..... I think

[warburp]

if anybody is still checking in here i got that math issue i was talking baout earlier fixed everything works but my function move take a long time to happen unless move is 1 how would i fix it

int move(int a, int b, int Turn, char Player)
{
	if (Turn >=0 && Turn <= 9)
	{
		
		while (((a*3)+(b+1)) != Turn)
		{
			while (((a*3)+(b+1)) != Turn && b <= 3)
			{
				b++;
			}
			a++;	

	}

[K0T4K0t4]

if you post the full new code ill run it and see whats causing it since you seemed to change quite a bit and even in that last chunk you seem to be missing a }(or they are misaligned and in the unposted section)

[TheIdeasMan]

for(int a = 0; a <= 3; a++) {
	for(int b = 0; b <= 3; b++) {
		square[a][b] = ' ';
        }
}

There is a problem with the subscripts going out of bounds. Use < not <=. The for loop ends when the end condition becomes false, so the following code stops when it reaches 2:

for(a = 0; a < 3; a++) {
	for(b = 0; b < 3; b++) {
		square[a][b] = ' ';
        }
}

Valid subscripts are 0, 1, 2.

Get into the habit of always using braces, even when there is only 1 statement following, it will save you one day when you add more code.

Also, you had already declared a & b, so no need to redeclare them in the for loop.

HTH

[TheIdeasMan]

while (((a*3)+(b+1)) != Turn && b <= 3

If Turn is 1 to 9, then this expression goes outside of that range for values of a or b larger than 2. This results in loops that keep going until the int overflows & becomes negative (about 2.1 billion ), then it keeps going until it gets to zero and then 1 at which point it does something. And you have 2 of these loops, so the loop executes at least 8.4 billion times.

So what was the purpose of the expression & why is it there twice?

Also, you have code to validate the Turn value before it calls the move function, so why do it again in the move function?

HTH

[warburp]

it was to find the proper spot on the array for the Turn input thank you for the clarification as to what was happening there i replaced it with

int Getb(int row, int Turn)
{
		int col = (Turn - row*3)-1;
		return col;
}

int Geta(int Turn)
{
		int row =  floor(float (Turn/3));
		return row;
}

now im trying to create an AI for the user to play against and well as you may have learned from reading this its tough for me lol

[TheIdeasMan]

You can convert Turn into row & col like this:

row = (Turn-1) / 3; // integer division no need for float answer is 0, 1, 2
col = (Turn-1) % 3; //remainder of division by 3  answer is 0, 1, 2 

This uses the Turn format:

123
456
789

[warburp]

i had tried what you suggested there but the issue i ran into is would round up and i needed it to always round down

[TheIdeasMan]

But my code works though - there is no need for rounding.

[Chervil]

Chervil wrote:

Instead of defining new variables in function move(), you could pass by reference the variables from main().

Notice the code subsequently posted here, this is passing the parameters by value, not by reference:
int move(int a, int b, int Turn, char Player)

The code should look like this:
int move(int &a, int &b, int Turn, char Player)

Just as important, the aim of that change is to ensure that a and b are properly initialised before being used. From the code posted above, I'm not reassured that the problem is resolved.

[warburp]

@TheIdeasman hmmm then you did something different from when i tried that i don't see

@Chervil the code does work now for two player purposes 'm trying to replace player two with an AI

[Chervil]

Maybe it does indeed work, the code may have changed completely since the earlier post. If you need any further help then it would be useful if you could post the current code.