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tic-tac-toe

Unbeatable Tic Tac Toe. Single-page HTML, CSS & JavaScript.

DEMO

tic-tac-toe

Implementation of Minimax algorithm wrapped up in a neat chalkboard UI. The chalk effect is achieved using SVG turbulence filters.

Minimax algorithm:

tic-tac-toe/index.html

Lines 438 to 482 in 3e10e64

function getComputerMoveData(tempPlaygroundState, depth) {
const winCombinationIndex = getWinCombinationIndex(tempPlaygroundState);
if (winCombinationIndex !== -1) {
// we've got a winner in this hypothetical game!
const wonMover = tempPlaygroundState[winCombinations[winCombinationIndex][0]];
return {
index: -1,
score: wonMover === 1
? -1 // user hypothetically won (bad)
: 1 // computer hypothetically won (good)
};
} else if (!tempPlaygroundState.some((mover) => mover === -1)) {
// a tie
return { index: -1, score: 0 };
}
depth = (depth || 0) + 1;
// 1 - user's hypothetical turn; 0 - computer's hypothetical turn.
const mover = +!(depth % 2);
const availableMoves = tempPlaygroundState
.map((_, i) => i)
.filter((boardIndex) => tempPlaygroundState[boardIndex] === -1);
const scores = [];
const moves = [];
for (let i = 0; i < availableMoves.length; i++) {
const move = availableMoves[i];
const iterationPlayground = [ ...tempPlaygroundState ];
iterationPlayground[move] = mover;
const hypotheticalMoveData = getComputerMoveData(iterationPlayground, depth);
scores.push(hypotheticalMoveData.score);
moves.push(move);
// rollback the hypothetical move
tempPlaygroundState[move] = -1;
}
const func = mover === 1
? Math.min // we're looking for the min score if it's user's turn
: Math.max; // and for the max score if it's computer's score
const moveScore = func.apply(null, scores);
const moveScoreIndex = scores.indexOf(moveScore);
return { index: moves[moveScoreIndex], score: moveScore };
}