20. Kółko i Krzyżyk (Tic-Tac-Toe)

const WINNING_COMBINATIONS = [
  [0, 1, 2], [3, 4, 5], [6, 7, 8], // wiersze
  [0, 3, 6], [1, 4, 7], [2, 5, 8], // kolumny
  [0, 4, 8], [2, 4, 6],             // przekątne
];

function checkWinner(squares) {
  for (const [a, b, c] of WINNING_COMBINATIONS) {
    if (squares[a] && squares[a] === squares[b] && squares[a] === squares[c]) {
      return { winner: squares[a], line: [a, b, c] };
    }
  }
  if (squares.every(Boolean)) return { winner: 'draw' };
  return null;
}

// Minimax dla AI (wariant C)
function minimax(squares, isMaximizing) {
  const result = checkWinner(squares);
  if (result?.winner === 'O') return 10;
  if (result?.winner === 'X') return -10;
  if (result?.winner === 'draw') return 0;

  if (isMaximizing) {
    let best = -Infinity;
    squares.forEach((_, i) => {
      if (!squares[i]) {
        squares[i] = 'O';
        best = Math.max(best, minimax(squares, false));
        squares[i] = null;
      }
    });
    return best;
  } else {
    let best = Infinity;
    squares.forEach((_, i) => {
      if (!squares[i]) {
        squares[i] = 'X';
        best = Math.min(best, minimax(squares, true));
        squares[i] = null;
      }
    });
    return best;
  }
}