C Chomp questions? - c

Question

I'm trying to create the game Chomp. I am halfway through but pretty stuck.
The game will have 5 different functions. Pointers and structs are not allowed.
This is how far I have come and I have been struggeling with a few problems for a while, but I can't figure out how to solve them by myself so I thought I could get some help here.
BUGS
a) If you first input 2 2 and then input 2 1 it will say that the position already has been eaten, even though it's a perfectly valid position to eat. Instead of checking if the position is != 'O' I should check if it is == 'O', but that won't work either because in the check_move() loop the row and col will not always be an O...
b) If you input a position that is not inside the matrix (i.e. 20 20) you will get two lines of errors. I don't understand why. Of course I only want to display one error, not two.
c) If you input a position that has already been eaten you will get the error "Already been eaten!" several times due to the loop that is looping through the print several times.
QUESTION
a) What is the best way to alternate between Player 1 and Player 2? I thought about an int that will increase by +1 every time a player makes a valid move. Then I will check if the value of the int is odd or even. Odd = Player 1 and even = Player 2 or vice verca. But that won't work because I'm not allowed to have any more global variables than I currently has. And I'm only allowed to return one value from one function (check_move()).
#include <stdio.h>
int height = 4;
int width = 10;
char matrix[4][10];
void initialize()
{
for(int row = 0; row < height; row++)
for(int col = 0; col < width; col++)
matrix[row][col] = 'O';
}
void print_board()
{
printf("\n\n");
for(int row = 0; row < height; row++)
{
for(int col = 0; col < width; col++)
{
printf("%c", matrix[row][col]);
}
printf("\n");
}
printf("\n\n");
}
void get_move(int player, int input[])
{
printf("Player %d, make your move: ", player);
scanf("%d %d", &input[0], &input[1]);
}
int check_move(int position[])
{
int row = position[0];
int col = position[1];
int status = 1;
if(row <= height && col <= width)
{
for(row; row <= height; row++)
{
for(col; col <= width; col++)
{
// Checks if position already has been eaten
if(matrix[row-1][col-1] != 'O')
{
printf("Already eaten!\n");
status = 0;
}
}
}
}
else if(row >= height || col >= width)
{
printf("Your move must be inside the matrix!\n");
status = 0;
}
return status;
}
void update_board(int x, int y)
{
for(int xi = x; xi <= 10; ++xi)
{
for(int yi = y; yi <= 10; ++yi)
matrix[xi-1][yi-1] = ' ';
}
}
int main(void)
{
int player = 1;
int position[2];
initialize();
print_board();
while(1){
get_move(player, position);
check_move(position);
while(check_move(position) != 1)
{
printf("Try again!\n\n");
get_move(player, position);
}
update_board(position[0], position[1]);
print_board();
}
getchar();
getchar();
getchar();
return 0;
}

Answer 1

Bug a and c:
Your check_move function is wrong, you should only test if the position played is eaten or not, the status of the other positions are not relevant:
int check_move(int pos[])
{
if(pos[0] < 1 || pos[0] > height || pos[1] < 1 || pos[1] > width)
{
printf("Your move must be inside the matrix!\n");
return 0;
}
if(matrix[ pos[0] - 1 ][ pos[1] - 1 ] != 'O' ) {
printf("Already eaten!\n");
return 0;
}
return 1;
}
Bug b:
You get the error message twice because you're calling check_move twice in your main:
check_move(position);
while(check_move(position) != 1)
Just remove the useless first call to check_move().
Question a:
You can switch between players by updating the variable player inside your main :
player = (player + 1) % maxNumberOfPlayer;
This will go from 0 to maxNumberOfPlayer - 1, so you may use printf("Player %d, make your move: ", player + 1); for a more user-friendly output. Also, if maxNumberOfPlayer = 2, player = (player + 1) % 2; is equivalent to player = !player.

Answer 2

In main, inside your while loop just add:
player = !player;
Which will toggle player between 0 and 1.