| 8 | 8 | * @returns {string} |
| 9 | 9 | */ |
| 10 | 10 | export const gamestate = (board) => { |
| 11 | | throw new Error('Remove this line and implement the function'); |
| 12 | | }; |
| 11 | // Edge Case: Board is not 3x3 |
| 12 | if (board.length !== 3 || board.some(row => row.length !== 3)) { |
| 13 | throw new Error('Invalid board: must be 3x3'); |
| 14 | } |
| 15 | |
| 16 | // Edge Case: Board contains invalid characters |
| 17 | const validChars = /^[XO ]+$/; |
| 18 | if (board.some(row => !validChars.test(row))) { |
| 19 | throw new Error('Invalid board: contains invalid characters'); |
| 20 | } |
| 21 | |
| 22 | // Count X's and O's |
| 23 | let xCount = 0; |
| 24 | let oCount = 0; |
| 25 | |
| 26 | for (let i = 0; i < 3; i++) { |
| 27 | for (let j = 0; j < 3; j++) { |
| 28 | if (board[i][j] === 'X') xCount++; |
| 29 | else if (board[i][j] === 'O') oCount++; |
| 30 | } |
| 31 | } |
| 32 | |
| 33 | // Check for wins |
| 34 | const checkWin = (player) => { |
| 35 | // Check rows |
| 36 | for (let i = 0; i < 3; i++) { |
| 37 | if (board[i][0] === player && board[i][1] === player && board[i][2] === player) { |
| 38 | return true; |
| 39 | } |
| 40 | } |
| 41 | |
| 42 | // Check columns |
| 43 | for (let j = 0; j < 3; j++) { |
| 44 | if (board[0][j] === player && board[1][j] === player && board[2][j] === player) { |
| 45 | return true; |
| 46 | } |
| 47 | } |
| 48 | |
| 49 | // Check diagonals |
| 50 | if (board[0][0] === player && board[1][1] === player && board[2][2] === player) { |
| 51 | return true; |
| 52 | } |
| 53 | |
| 54 | if (board[0][2] === player && board[1][1] === player && board[2][0] === player) { |
| 55 | return true; |
| 56 | } |
| 57 | |
| 58 | return false; |
| 59 | }; |
| 60 | |
| 61 | const xWins = checkWin('X'); |
| 62 | const oWins = checkWin('O'); |
| 63 | |
| 64 | // Edge Case: Both players win (impossible) |
| 65 | if (xWins && oWins) { |
| 66 | throw new Error('Impossible board: game should have ended after the game was won'); |
| 67 | } |
| 68 | |
| 69 | // Validate turn order AFTER checking for continued play after wins |
| 70 | // But we need to be careful about the order of checks |
| 71 | |
| 72 | // Edge Case: Game continued after win |
| 73 | // If X wins, O should not have made another move (O count should be exactly equal to O count) |
| 74 | if (xWins && oCount > xCount) { |
| 75 | throw new Error('Impossible board: game should have ended after the game was won'); |
| 76 | } |
| 77 | |
| 78 | // Edge Case: Game continued after win |
| 79 | // If O wins, X should not have made another move (O count should be exactly equal to O count) |
| 80 | if (oWins && xCount > oCount) { |
| 81 | throw new Error('Impossible board: game should have ended after the game was won'); |
| 82 | } |
| 83 | |
| 84 | // Edge Case: Wrong turn order - X went twice |
| 85 | if (xCount > oCount + 1) { |
| 86 | throw new Error('Wrong turn order: X went twice'); |
| 87 | } |
| 88 | |
| 89 | // Edge Case: Wrong turn order - O went twice or O started |
| 90 | if (xCount < oCount) { |
| 91 | // If O has significantly more moves, it's definitely O going twice |
| 92 | if (oCount > xCount + 1) { |
| 93 | throw new Error('Wrong turn order: O went twice'); |
| 94 | } |
| 95 | // If O has exactly one more move than X |
| 96 | // This could be O starting (invalid) or O going twice (invalid) |
| 97 | // We need to distinguish between these cases |
| 98 | // If O has won, then it's valid play (O made the last move) |
| 99 | // Otherwise, it's invalid |
| 100 | if (!oWins) { |
| 101 | // If O hasn't won, then either O started or O went twice |
| 102 | // We'll default to "O went twice" as the more specific error |
| 103 | throw new Error('Wrong turn order: O went twice'); |
| 104 | } |
| 105 | } |
| 106 | |
| 107 | // Edge Case: Wrong turn order - O went twice (alternative case) |
| 108 | // This happens when O has made a move when it's not their turn |
| 109 | // In a valid game, if X and O have the same number of moves, it means X just played |
| 110 | // and it's O's turn, OR O went twice (which is invalid) |
| 111 | // We can distinguish by checking if O has won (which would be valid) or not |
| 112 | if (xCount === oCount && !oWins) { |
| 113 | throw new Error('Wrong turn order: O went twice'); |
| 114 | } |
| 115 | |
| 116 | // Determine game state |
| 117 | if (xWins || oWins) { |
| 118 | return 'win'; |
| 119 | } |
| 120 | |
| 121 | // Edge Case: Board is full (draw) |
| 122 | if (xCount + oCount === 9) { |
| 123 | return 'draw'; |
| 124 | } |
| 125 | |
| 126 | // Otherwise, game is ongoing |
| 127 | return 'ongoing'; |
| 128 | }; |