Is there a way to implement AI to the computer in TicTacToe? - c++

Question

I have this program that runs the game of Tictactoe, but i'd like to add AI to the computer function so it can be more difficult in order to play with
I tried by rand(); but it just make the computer put the decision in whatever slot is available.
void ia_turn(){
while (true){
int ia_tu = (rand() % 9) +1;
int ia_op = ia_tu - 1;
int row = ia_op / 3;
int column = ia_op % 3;
char matrix_pos = matrix[row][column];
if (matrix_pos == 'X' || matrix_pos == 'O'){
continue;
}else{
cout << "The AI selected the position: "<<ia_tu<<endl;
matrix[row][column] = 'O';
break;
}
}
}
I expect the movements of the ComputerAI to block my movements, but it can't be done with the rand() function.
This is the checking for wins function that i have
void checking_for_wins(){
const char* wins_possibilities[8] = {"123","456","789","159","753","147","258","369"};
for (int i =0;i<8;i++){
bool win = true;
char prev_op = '0';
const char* win_possibility = wins_possibilities[i]; //funciona como puntero en caso de que se cumpla uno de las wins_possibilities[]
for (int rcl = 0;rcl<dim_m;rcl++){
char alphaChar = win_possibility[rcl];
int intr_number = alphaChar - '0';
int op_sp = intr_number - 1;
int row = op_sp / dim_m; //busca la posición de la fila
int column = op_sp % dim_m; //busca la posición de la columna
char current_op = matrix[row][column];
if (prev_op == '0'){
prev_op = current_op;
}else if (prev_op == current_op){
continue;
}else{
win = false;
break;
}
}
if (win){
cout << "Felicidades, ganaste!! \n";
cout << "El jugador "<<prev_op<<" gana, felicidades! \n";
exit(0);
break;
}
}
}

Answer 1

The best way to start is to write a function which looks for possible victories (instead of looking to see if there are three in a row, check to see if there are two in a row instead). Then have the function return the space that would be a victory and have the AI move there instead. Ex: If the matrix looks like
X X _
_ _ _
_ O O
Have the function return 0,2 and 2,0.
Then have your AI pick from that randomly.
After that you can modify that function to return who's possible victory it is, and then have your AI always prefer to go where it would win.
Implementation can look something like this:
#include <vector> // Vector comes from this
#include <utility> // Pair comes from this
std::vector<std::pair<bool, Point>> GetPossibleVictories()
{
std::vector<std::pair<bool, Point>> retVal;
// Check for two in a row Horitzontally, Vertically, and Diagonally.
{
if (/*IsPossibleWin*/)
{
retVal.push_back(std::pair<bool, Point>(isAIsVictory, Point{ X, Y }));
}
}
return retVal;
}
In addition I would also investigate more modern C++ constructs which can help you such as containers (std::vector, std::list, std::set, and etc) which can help you store your matrix in a easier to manipulate way.
In the example above I'm using a custom type (Point) which in its simplest way can be programmed like this:
struct Point
{
int X = 0;
int Y = 0;
};
By using a struct (or a class where every member is public by default) you can store coordinates for your matrix in a single object. In addition I'm using a vector which acts like a automatically resizing array. You can go through each thing in the vector like this:
for(const auto& possibleWin : possibleWins) // possibleWins is the vector returned from the previous example.
{
// possibleWin in this block will be the same value as if you used a for loop and did possibleWins[x]
}
Finally the example above uses Pair, which just holds two different types of things. It can be used as follows:
std::pair<bool, Point> myPair;
myPair.first = true;
myPair.second = Point{0, 2};
For more reading (Scroll to the bottom for examples on how to use them):
Vector
Pair
Hopefully this can give you some ideas on how to start making your AI a little smarter.