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/*
O | | X
---------
X | | X
---------
| O | O
// || \\
O | X | X O | | X O | | X
--------- --------- ---------
X | | X X | X | X X | | X
--------- --------- ---------
| O | O | O | O X | O | O
// \\ // \\
O | X | X O | X | X O | O | X O | | X
--------- --------- --------- ---------
X | O | X X | | X X | | X X | O | X
--------- --------- --------- ---------
| O | O O | O | O X | O | O X | O | O
//
O | O | X
---------
X | X | X
---------
O | O | O
*/
// this is the board flattened and filled with some values to easier asses the Artificial Inteligence.
var origBoard = ["O",1 ,"X","X",4 ,"X", 6 ,"O","O"];
// human
var huPlayer = "O";
// ai
var aiPlayer = "X";
// keep track of function calls
var fc = 0;
// finding the ultimate play on the game that favors the computer
var bestSpot = minimax(origBoard, aiPlayer);
//loging the results
console.log("index: " + bestSpot.index);
console.log("function calls: " + fc);
// the main minimax function
function minimax(newBoard, player){
//keep track of function calls;
fc++;
//available spots
var availSpots = emptyIndexies(newBoard);
// checks for the terminal states such as win, lose, and tie and returning a value accordingly
if (winning(newBoard, huPlayer)){
return {score:-10};
}
else if (winning(newBoard, aiPlayer)){
return {score:10};
}
else if (availSpots.length === 0){
return {score:0};
}
// an array to collect all the objects
var moves = [];
// loop through available spots
for (var i = 0; i < availSpots.length; i++){
//create an object for each and store the index of that spot that was stored as a number in the object's index key
var move = {};
move.index = newBoard[availSpots[i]];
// set the empty spot to the current player
newBoard[availSpots[i]] = player;
//if collect the score resulted from calling minimax on the opponent of the current player
if (player == aiPlayer){
var result = minimax(newBoard, huPlayer);
move.score = result.score;
}
else{
var result = minimax(newBoard, aiPlayer);
move.score = result.score;
}
//reset the spot to empty
newBoard[availSpots[i]] = move.index;
// push the object to the array
moves.push(move);
}
// if it is the computer's turn loop over the moves and choose the move with the highest score
var bestMove;
if(player === aiPlayer){
var bestScore = -10000;
for(var i = 0; i < moves.length; i++){
if(moves[i].score > bestScore){
bestScore = moves[i].score;
bestMove = i;
}
}
}else{
// else loop over the moves and choose the move with the lowest score
var bestScore = 10000;
for(var i = 0; i < moves.length; i++){
if(moves[i].score < bestScore){
bestScore = moves[i].score;
bestMove = i;
}
}
}
// return the chosen move (object) from the array to the higher depth
return moves[bestMove];
}
// returns the available spots on the board
function emptyIndexies(board){
return board.filter(s => s != "O" && s != "X");
}
// winning combinations using the board indexies for instace the first win could be 3 xes in a row
function winning(board, player){
if (
(board[0] == player && board[1] == player && board[2] == player) ||
(board[3] == player && board[4] == player && board[5] == player) ||
(board[6] == player && board[7] == player && board[8] == player) ||
(board[0] == player && board[3] == player && board[6] == player) ||
(board[1] == player && board[4] == player && board[7] == player) ||
(board[2] == player && board[5] == player && board[8] == player) ||
(board[0] == player && board[4] == player && board[8] == player) ||
(board[2] == player && board[4] == player && board[6] == player)
) {
return true;
} else {
return false;
}
}
Also see: Tab Triggers