How can I store an array slot to use between functions? - arrays

Question

I'm trying to make a tic tac toe game that allows you to play against a human enemy or the computer. I'm trying to code some basic AI that will prevent you from winning by scanning the board to see if you have 2 X's or O's next to each other or in opposite corners in a column/row/diagonal and I need a way to tell the computer if and which tile it needs to print on to prevent you from winning. My code:
#include<stdio.h>
#include<stdlib.h>
#include<time.h>
void initializeBoard(); //initialize the board //
void drawBoard(); //draw it on the window //
void player_1_move(); //check if player 1 made a valid move and update the board
void player_2_move(); //check if player 2 made a valid move and update the board
//AI functions
void pickTile(); //picks a tile based on available information
void computerTurn(); //checks if the computer is going first or second
char* isThereaWinningMove(); //checks if the user is abou to win
char tempcT;
int checkWin(); //checks if either player has won at the end of every turn and if so ends the game and declares a winner //
char board[3][3]; //3x3 tic tac toe board
int main(){
int win = 0;
printf("==============");
printf("\n TIC TAC TOE \n");
printf("==============\n");
printf("The World's Number 1 Multiplayer Game! \n\n");
initializeBoard();
//let's the user pick the gamemode
int x;
printf("Press 1 to PLAY AGAINST A HUMAN or 0 to PLAY AGAINST AI: \n");
scanf("%d", &x);
while(x!=0 && x!=1){
printf("Invalid input. Press 1 to PLAY AGAINST A HUMAN or 0 to PLAY AGAINST AI: ");
scanf("%d", &x);
}
if(x==1){ //pvp
do{
drawBoard();
printf("\n\n");
player_1_move(); //player 1 (X) moves
drawBoard(); //update the board with each move
win=checkWin(); //did player 1 win?
if(win==1){
printf("\nPlayer 1 has won!");
break;
}
printf("\n\n");
player_2_move(); //player 2 (O) moves
drawBoard(); //update the board with each move
win=checkWin(); //did player 2 win?
if(win==1){
printf("\nPlayer 2 has won!");
break;
}
}while(1);
}
else{ //pvc
computerTurn();
if(tempcT == 'O'){ //if the player is going first
do{
srand( (unsigned int) time(NULL) ); //initialize random seed
drawBoard();
printf("\n\n");
player_1_move(); //user (X) moves first
drawBoard(); //update the board with each move
win=checkWin(); //did player 1 win?
if(win==1){
printf("\nPlayer has won!");
break;
}
//computer turn
printf("\n\n");
pickTile(); //picks available tile
win=checkWin();
if(win == 1){
printf("\nI win!");
break;
}
}while(1);
}
else{ //if the computer goes first
do{
//computer turn
srand( (unsigned int) time(NULL) ); //initialize random seed
printf("\n\n");
pickTile(); //picks available tile
win=checkWin();
if(win == 1){
printf("\nI win!");
break;
}
//player turn
drawBoard();
printf("\n\n");
player_1_move(); //user (X) moves first
drawBoard(); //update the board with each move
win=checkWin(); //did player 1 win?
if(win==1){
printf("\nPlayer has won!");
break;
}
}while(1);
}
}
return 0;
}
//initialize the board
void initializeBoard(){
int i, j;
for(i=0; i<=2; i++){
for(j=0; j<=2; j++){
board[i][j]= ' ';
}
}
}
//draws the board on the window
void drawBoard(){
int t;
for(t=0; t<=2; t++){
printf(" %c | %c | %c ", board[t][0], board[t][1], board[t][2]);
if(t!=2){
printf("\n---|---|---\n");
}
}
printf("\n");
}
//checks if there is a winner at the end of every turn
int checkWin(){
int i;
//checks rows
for(i=0; i<=2; i++){
if(board[i][0]==board[i][1] && board[i][0]==board[i][2] && board[i][0]!= ' '){
return 1;
}
}
//checks columns
for(i=0; i<=2; i++){
if(board[0][i]==board[1][i] && board[0][i]==board[2][i] && board[0][i]!= ' '){
return 1;
}
}
//checks diagonals from top left to bottom right
for(i=0; i<=2; i++){
if(board[0][0]==board[1][1] && board[1][1]==board[2][2] && board[0][0]!= ' '){
return 1;
}
}
//checks diagonals from bottom left to top right
for(i=0; i<=2; i++){
if(board[2][0]==board[1][1] && board[1][1]==board[0][2] && board [2][0]!= ' '){
return 1;
}
}
return 0;
}
//player 1 (X) move
void player_1_move(){
int x, y;
//player 1 picks coordinates on the board
printf("Player 1, please pick a row (1-3): ");
scanf("%d", &x);
printf("Now pick a column (1-3): ");
scanf("%d", &y);
x--, y--;
//check if it's a valid tile
while(1){
if(x<0 || x>2){
if(y<0 || y>2){
printf("Invalid tile, please enter a valid tile (same order as before, 1-3): ");
scanf("%d%d", &x, &y);
x--, y--;
}
else{
printf("Invalid row, please try again (1-3): ");
scanf("%d", &x);
x--;
}
}
else if(y<0 || y>2){
printf("Invalid column, please try again (1-3): ");
scanf("%d", &y);
y--;
}
else{
break;
}
}
//check if the tile is free
while(board[x][y]=='O' || board[x][y]=='X'){
printf("Invalid move, please enter valid coordinates (same order as before, 1-3): ");
scanf("%d%d", &x, &y);
x--, y--;
}
board[x][y]='X';
}
//player 2 (O) move
void player_2_move(){
int x, y;
//player 2 picks a tile
printf("Player 2, please pick a row (1-3): ");
scanf("%d", &x);
printf("Now pick a column (1-3): ");
scanf("%d", &y);
x--, y--;
//check if it's a valid tile
while(1){
if(x<0 || x>2){
if(y<0 || y>2){
printf("Invalid tile, please enter a valid tile (same order as before, 1-3): ");
scanf("%d%d", &x, &y);
x--, y--;
}
else{
printf("Invalid row, please try again (1-3): ");
scanf("%d", &x);
x--;
}
}
else if(y<0 || y>2){
printf("Invalid column, please try again (1-3): ");
scanf("%d", &y);
y--;
}
else{
break;
}
}
//check if the tile is free
while(board[x][y]=='O' || board[x][y]=='X'){
printf("Invalid move, please enter valid coordinates (same order as before, 1-3): ");
scanf("%d%d", &x, &y);
x--, y--;
}
board[x][y]='O';
}
//AI functions
//checks if the computer is going first or second
void computerTurn(){
int x;
printf("Press 1 if you'd like to GO FIRST and 0 if you'd like to GO SECOND: ");
scanf("%d", &x);
while(x!=0 && x!=1){
printf("Invalid input. Press 1 if you'd like to GO FIRST and 0 if you'd like to GO SECOND: ");
scanf("%d", &x);
}
if(x==1){
printf("OK, the player is going first.\n\n");
tempcT = 'O';
}
else{
printf("OK, I'm going first.\n\n");
tempcT = 'X';
}
}
//if there is a winning move available on the AI's turn
char* isThereaWinningMove(){
int i;
//checks rows
for(i=0; i<=2; i++){
if(board[i][0]==board[i][1] && board[i][1] == ' '){
return &board[i][2];
}
}
for(i=0; i<=2; i++){
if(board[i][0]==board[i][2] && board[i][1] == ' '){
return &board[i][1];
}
}
for(i=0; i<=2; i++){
if(board[i][1]==board[i][2] && board[i][0] == ' '){
return &board[i][0];
}
}
//checks columns
for(i=0; i<=2; i++){
if(board[0][i]==board[2][i] && board[1][i] == ' '){
return &board[1][i];
}
}
for(i=0; i<=2; i++){
if(board[0][i]==board[1][i] && board[2][i] == ' '){
return &board[2][i];
}
}
for(i=0; i<=2; i++){
if(board[1][i]==board[2][i] && board[0][i] == ' '){
return &board[0][i];
}
}
//checks diagonals from top left to bottom right
if(board[1][1]==board[2][2] && board[0][0] == ' '){
return &board[0][0];
}
if(board[0][0]==board[2][2] && board[1][1] == ' '){
return &board[1][1];
}
if(board[0][0]==board[1][1] && board[2][2] == ' '){
return &board[2][2];
}
//checks diagonals from bottom left to top right
if(board[1][1]==board[0][2] && board [2][0] == ' '){
return &board[2][0];
}
if(board[2][0]==board[1][1] && board [0][2] ==' '){
return &board[0][2];
}
if(board[2][0]==board[0][2] && board [1][1] == ' '){
return &board[1][1];
}
return 0;
}
//picks a tile based on available information
void pickTile(){
int rndX, rndY;
char *p = isThereaWinningMove();
//did the computer detect a winning move?
if(p != 0){
*p = tempcT;
}
//if not, pick a random available tile
else{
while(1){
rndX = rand()%3;
rndY = rand()%3;
if(board[rndX][rndY] == ' '){
board[rndX][rndY] = tempcT;
break;
}
}
}
}
Playing against a human seems to work just fine. I only have a problem with assigning tempcT's value to whatever array slot the isThereaWinningMove function will return. The code I've written now only doesn't actually run because of 2 compiler errors:
[Error] assignment of function 'char isThereaWinningMove()'
[Error] cannot convert 'int' to 'char()' in assignment

Answer 1

As I said through remarks to your question :
[Error] assignment of function 'char isThereaWinningMove()' [Error] cannot convert 'int' to 'char()' in assignment
isThereaWinningMove is a function, doing isThereaWinningMove = 'tempcT' you try to assign a function with an (invalid) char which as no sense.
Some other remarks :
Out of that you have several calls of isThereaWinningMove done for nothing because you loose the result.
scanf("%d", x)is invalid you wanted scanf("%d", &x)
You call srand several times with very probably the same value (program runs in the same second), so you very probably get the same value for all your rndX and rndY, you must call srand one time at the beginning of main.
In fact you want to modify the cell whose value is return by isThereaWinningMove, in C (and then C++) you can return the address of the cell rather than the cell value :
char * isThereaWinningMove(); //checks if there is a winning move available
...
char * isThereaWinningMove(){
int i;
//checks rows
for(i=0; i<=2; i++){
if(board[i][0]==board[i][1] && board[i][0]!= ' '){
return &board[i][2];
}
}
for(i=0; i<=2; i++){
if(board[i][0]==board[i][2] && board[i][0]!= ' '){
return &board[i][1];
}
}
for(i=0; i<=2; i++){
if(board[i][1]==board[i][2] && board[i][0]!= ' '){
return &board[i][0];
}
}
//checks columns
for(i=0; i<=2; i++){
if(board[0][i]==board[2][i] && board[0][i]!= ' '){
return &board[1][i];
}
}
for(i=0; i<=2; i++){
if(board[0][i]==board[1][i] && board[0][i]!= ' '){
return &board[2][i];
}
}
for(i=0; i<=2; i++){
if(board[1][i]==board[2][i] && board[0][i]!= ' '){
return &board[0][i];
}
}
//checks diagonals from top left to bottom right
if(board[1][1]==board[2][2] && board[0][0]!= ' '){
return &board[0][0];
}
if(board[0][0]==board[2][2] && board[0][0]!= ' '){
return &board[1][1];
}
if(board[0][0]==board[1][1] && board[0][0]!= ' '){
return &board[2][2];
}
//checks diagonals from bottom left to top right
if(board[1][1]==board[0][2] && board [2][0]!= ' '){
return &board[2][0];
}
if(board[2][0]==board[1][1] && board [2][0]!= ' '){
return &board[0][2];
}
if(board[2][0]==board[0][2] && board [2][0]!= ' '){
return &board[1][1];
}
return 0;
}
...
void pickTile(){
int rndX, rndY, i;
//did the computer detect a winning move?
char * p = isThereaWinningMove();
if(p != 0){
*p = tempcT;
}
//if not, pick a random available tile
else{
...
an other way is to do the assignment in isThereaWinningMove and return something else that 0 when you did
int isThereaWinningMove(); //checks if there is a winning move available
...
int isThereaWinningMove(){
int i;
//checks rows
for(i=0; i<=2; i++){
if(board[i][0]==board[i][1] && board[i][0]!= ' '){
board[i][2] = tempcT;
return 1;
}
}
for(i=0; i<=2; i++){
if(board[i][0]==board[i][2] && board[i][0]!= ' '){
board[i][1] = tempcT;
return 1;
}
}
for(i=0; i<=2; i++){
if(board[i][1]==board[i][2] && board[i][0]!= ' '){
board[i][0] = tempcT;
return 1;
}
}
//checks columns
for(i=0; i<=2; i++){
if(board[0][i]==board[2][i] && board[0][i]!= ' '){
board[1][i] = tempcT;
return 1;
}
}
for(i=0; i<=2; i++){
if(board[0][i]==board[1][i] && board[0][i]!= ' '){
board[2][i] = tempcT;
return 1;
}
}
for(i=0; i<=2; i++){
if(board[1][i]==board[2][i] && board[0][i]!= ' '){
board[0][i] = tempcT;
return 1;
}
}
//checks diagonals from top left to bottom right
if(board[1][1]==board[2][2] && board[0][0]!= ' '){
board[0][0] = tempcT;
return 1;
}
if(board[0][0]==board[2][2] && board[0][0]!= ' '){
board[1][1] = tempcT;
return 1;
}
if(board[0][0]==board[1][1] && board[0][0]!= ' '){
board[2][2] = tempcT;
return 1;
}
//checks diagonals from bottom left to top right
if(board[1][1]==board[0][2] && board [2][0]!= ' '){
board[2][0] = tempcT;
return 1;
}
if(board[2][0]==board[1][1] && board [2][0]!= ' '){
board[0][2] = tempcT;
return 1;
}
if(board[2][0]==board[0][2] && board [2][0]!= ' '){
board[1][1] = tempcT;
return 1;
}
return 0;
}
...
//picks a tile based on available information
void pickTile(){
int rndX, rndY, i;
//did the computer detect a winning move?
if (isThereaWinningMove() == 0){
//if not, pick a random available tile
while(1){
...
Whatever the way to do, also removing the useless variable i in pickTile and removing the calls of isThereaWinningMove in main some other problems appear at the execution, for instance I can have :
pi#raspberrypi:/tmp $ gcc -Wall t.cpp
pi#raspberrypi:/tmp $ ./a.out
TIC TAC TOE
The World's Number 1 Multiplayer Game!
Press 1 to PLAY AGAINST A HUMAN or 0 to PLAY AGAINST AI: 0
Press 1 if you'd like to GO FIRST and 0 if you'd like to GO SECOND: 1
OK, the player is going first. | |
---|---|---
| |
---|---|---
| |
Player 1, please pick a row (1-3): 2
Now pick a column (1-3): 2
| |
---|---|---
| X |
---|---|---
| |
| |
---|---|---
| X |
---|---|---
O | |
Player 1, please pick a row (1-3): 1
Now pick a column (1-3): 1
X | |
---|---|---
| X |
---|---|---
O | |
O | |
---|---|---
| X |
---|---|---
O | |
Player 1, please pick a row (1-3): ^C
pi#raspberrypi:/tmp $
As you can see the program got the cell 1-1 I got before it.
The reason is simple, isThereaWinningMove` can get a cell without checking it is free, so for instance
if(board[i][0]==board[i][1] && board[i][0]!= ' '){
board[i][2] = tempcT;
return 1;
}
must be
if((board[i][0]==board[i][1] && board[i][0]!= ' ') && (board[i][2] == ' ')) {
board[i][2] = tempcT;
return 1;
}
etc
Note there are also two wrong indexes, for instance using the second way for
for(i=0; i<=2; i++){
if(board[i][1]==board[i][2] && board[i][0]!= ' '){
board[i][0] = tempcT;
return 1;
}
}
you wanted (out of the missing test checking the cell is empty)
for(i=0; i<=2; i++){
if(board[i][1]==board[i][2] && board[i][1]!= ' '){
board[i][0] = tempcT;
return 1;
}
}
and for
for(i=0; i<=2; i++){
if(board[1][i]==board[2][i] && board[0][i]!= ' '){
board[0][i] = tempcT;
return 1;
}
}
you wanted (out of the missing test checking the cell is empty) :
for(i=0; i<=2; i++){
if(board[1][i]==board[2][i] && board[1][i]!= ' '){
board[0][i] = tempcT;
return 1;
}
}
Note in checkWin the loops are useless in :
//checks diagonals from top left to bottom right
for(i=0; i<=2; i++){
if(board[0][0]==board[1][1] && board[1][1]==board[2][2] && board[0][0]!= ' '){
return 1;
}
}
//checks diagonals from bottom left to top right
for(i=0; i<=2; i++){
if(board[2][0]==board[1][1] && board[1][1]==board[0][2] && board [2][0]!= ' '){
return 1;
}
}
it is enough to do
if(board[0][0]==board[1][1] && board[1][1]==board[2][2] && board[0][0]!= ' '){
return 1;
}
if(board[2][0]==board[1][1] && board[1][1]==board[0][2] && board [2][0]!= ' '){
return 1;
}