| 4 | 4 | // |
| 5 | 5 | |
| 6 | 6 | /** |
| 7 | | * @param {string[]} board |
| 8 | | * @returns {string} |
| 7 | * Determines the state of a Tic Tac Toe game based on the given board. |
| 8 | * |
| 9 | * @param {string[]} board - An array of 3 strings, each representing a row of the board |
| 10 | * @returns {string} - Returns 'win', 'draw', or 'ongoing' based on the game state |
| 11 | * @throws {Error} - Throws an error for invalid board states with specific messages |
| 9 | 12 | */ |
| 10 | 13 | export const gamestate = (board) => { |
| 11 | | throw new Error('Remove this line and implement the function'); |
| 12 | | }; |
| 14 | // Validate board structure |
| 15 | if (!Array.isArray(board) || board.length !== 3) { |
| 16 | throw new Error('Invalid board: must have 3 rows'); |
| 17 | } |
| 18 | |
| 19 | for (const row of board) { |
| 20 | if (typeof row !== 'string' || row.length !== 3) { |
| 21 | throw new Error('Invalid board: each row must be a string of length 3'); |
| 22 | } |
| 23 | } |
| 24 | |
| 25 | // Count X's and O's |
| 26 | let xCount = 0; |
| 27 | let oCount = 0; |
| 28 | |
| 29 | for (const row of board) { |
| 30 | for (const cell of row) { |
| 31 | if (cell === 'X') xCount++; |
| 32 | else if (cell === 'O') oCount++; |
| 33 | else if (cell !== ' ') { |
| 34 | throw new Error('Invalid board: contains invalid characters'); |
| 35 | } |
| 36 | } |
| 37 | } |
| 38 | |
| 39 | // Edge Case: Invalid turn order - O started (only when O has 1 and X has 0) |
| 40 | if (oCount === 1 && xCount === 0) { |
| 41 | throw new Error('Wrong turn order: O started'); |
| 42 | } |
| 43 | |
| 44 | // Edge Case: Invalid turn order - O went twice in a row |
| 45 | if (oCount > xCount && oCount > 1) { |
| 46 | throw new Error('Wrong turn order: O went twice'); |
| 47 | } |
| 48 | |
| 49 | // Edge Case: Invalid turn order - X went twice in a row |
| 50 | if (xCount > oCount + 1) { |
| 51 | throw new Error('Wrong turn order: X went twice'); |
| 52 | } |
| 53 | |
| 54 | // Check for wins |
| 55 | const winPatterns = [ |
| 56 | // Rows |
| 57 | [0, 1, 2], |
| 58 | [3, 4, 5], |
| 59 | [6, 7, 8], |
| 60 | // Columns |
| 61 | [0, 3, 6], |
| 62 | [1, 4, 7], |
| 63 | [2, 5, 8], |
| 64 | // Diagonals |
| 65 | [0, 4, 8], |
| 66 | [2, 4, 6] |
| 67 | ]; |
| 68 | |
| 69 | // Convert board to flat array for easier checking |
| 70 | const flatBoard = board.join('').split(''); |
| 71 | |
| 72 | let xWins = false; |
| 73 | let oWins = false; |
| 74 | |
| 75 | for (const pattern of winPatterns) { |
| 76 | const [a, b, c] = pattern; |
| 77 | if (flatBoard[a] === 'X' && flatBoard[b] === 'X' && flatBoard[c] === 'X') { |
| 78 | xWins = true; |
| 79 | } |
| 80 | if (flatBoard[a] === 'O' && flatBoard[b] === 'O' && flatBoard[c] === 'O') { |
| 81 | oWins = true; |
| 82 | } |
| 83 | } |
| 84 | |
| 85 | // Edge Case: Both players win (impossible in a valid game) |
| 86 | if (xWins && oWins) { |
| 87 | throw new Error('Impossible board: game should have ended after the game was won'); |
| 88 | } |
| 89 | |
| 90 | // Edge Case: Game continued after win |
| 91 | // X wins but O made the same or more moves (X should have exactly one more) |
| 92 | if (xWins && xCount !== oCount + 1) { |
| 93 | throw new Error('Impossible board: game should have ended after the game was won'); |
| 94 | } |
| 95 | |
| 96 | // Edge Case: Game continued after win |
| 97 | // O wins but X made more moves (both should have the same number) |
| 98 | if (oWins && xCount !== oCount) { |
| 99 | throw new Error('Impossible board: game should have ended after the game was won'); |
| 100 | } |
| 101 | |
| 102 | // Determine game state |
| 103 | if (xWins || oWins) { |
| 104 | return 'win'; |
| 105 | } |
| 106 | |
| 107 | // Edge Case: Board is full (draw) |
| 108 | if (xCount + oCount === 9) { |
| 109 | return 'draw'; |
| 110 | } |
| 111 | |
| 112 | // Edge Case: Game is still ongoing |
| 113 | return 'ongoing'; |
| 114 | |
| 115 | // Handled Edge Cases: |
| 116 | // - Invalid turn order (O started) |
| 117 | // - Invalid turn order (X went twice) |
| 118 | // - Both players winning |
| 119 | // - Game continued after win (X won but O played) |
| 120 | // - Game continued after win (O won but X played) |
| 121 | // - Board is full (draw) |
| 122 | // - Game is still ongoing |
| 123 | }; |