| 1 | /* eslint-disable max-len */ |
| 1 | 2 | // |
| 2 | 3 | // This is only a SKELETON file for the 'State of Tic Tac Toe' exercise. It's been provided as a |
| 3 | 4 | // convenience to get you started writing code faster. |
| 4 | 5 | // |
| 5 | 6 | |
| 6 | 7 | /** |
| 7 | | * @param {string[]} board |
| 8 | | * @returns {string} |
| 8 | * Determines the state of a Tic-Tac-Toe game based on the given board. |
| 9 | * |
| 10 | * @param {string[]} board - An array of 3 strings, each representing a row of the 3x3 board. |
| 11 | * Each character in the string is either 'X', 'O', or ' ' (empty). |
| 12 | * @returns {string} - Returns one of the following states: |
| 13 | * 'win' - if a player has won the game |
| 14 | * 'draw' - if the game ended in a draw |
| 15 | * 'ongoing' - if the game is still in progress |
| 16 | * @throws {Error} - Throws an error with a specific message if the board is invalid. |
| 17 | * Possible error messages: |
| 18 | * - 'Wrong turn order: O started' - if O makes the first move |
| 19 | * - 'Wrong turn order: X went twice' - if X plays twice in a row |
| 20 | * - 'Impossible board: game should have ended after the game was won' - if moves are made after a win |
| 9 | 21 | */ |
| 10 | 22 | export const gamestate = (board) => { |
| 11 | | throw new Error('Remove this line and implement the function'); |
| 23 | // Validate board structure |
| 24 | if (!Array.isArray(board) || board.length !== 3) { |
| 25 | throw new Error('Invalid board: must be an array of 3 strings'); |
| 26 | } |
| 27 | |
| 28 | for (let i = 0; i < 3; i++) { |
| 29 | if (typeof board[i] !== 'string' || board[i].length !== 3) { |
| 30 | throw new Error('Invalid board: each row must be a string of length 3'); |
| 31 | } |
| 32 | } |
| 33 | |
| 34 | // Count X's and O's |
| 35 | let xCount = 0; |
| 36 | let oCount = 0; |
| 37 | |
| 38 | for (let i = 0; i < 3; i++) { |
| 39 | for (let j = 0; j < 3; j++) { |
| 40 | const char = board[i][j]; |
| 41 | if (char === 'X') { |
| 42 | xCount++; |
| 43 | } else if (char === 'O') { |
| 44 | oCount++; |
| 45 | } else if (char !== ' ') { |
| 46 | throw new Error('Invalid board: contains invalid characters'); |
| 47 | } |
| 48 | } |
| 49 | } |
| 50 | |
| 51 | // Edge Case: Invalid turn order - O started the game |
| 52 | if (oCount > xCount) { |
| 53 | throw new Error('Wrong turn order: O started'); |
| 54 | } |
| 55 | |
| 56 | // Edge Case: Invalid turn order - X went twice in a row (more than one turn difference) |
| 57 | if (xCount > oCount + 1) { |
| 58 | throw new Error('Wrong turn order: X went twice'); |
| 59 | } |
| 60 | |
| 61 | // Check for wins |
| 62 | const checkWin = (player) => { |
| 63 | // Check rows |
| 64 | for (let i = 0; i < 3; i++) { |
| 65 | if (board[i][0] === player && board[i][1] === player && board[i][2] === player) { |
| 66 | return true; |
| 67 | } |
| 68 | } |
| 69 | |
| 70 | // Check columns |
| 71 | for (let j = 0; j < 3; j++) { |
| 72 | if (board[0][j] === player && board[1][j] === player && board[2][j] === player) { |
| 73 | return true; |
| 74 | } |
| 75 | } |
| 76 | |
| 77 | // Check diagonals |
| 78 | if (board[0][0] === player && board[1][1] === player && board[2][2] === player) { |
| 79 | return true; |
| 80 | } |
| 81 | if (board[0][2] === player && board[1][1] === player && board[2][0] === player) { |
| 82 | return true; |
| 83 | } |
| 84 | |
| 85 | return false; |
| 86 | }; |
| 87 | |
| 88 | const xWins = checkWin('X'); |
| 89 | const oWins = checkWin('O'); |
| 90 | |
| 91 | // Edge Case: Both players win (impossible in a valid game) |
| 92 | if (xWins && oWins) { |
| 93 | throw new Error('Impossible board: game should have ended after the game was won'); |
| 94 | } |
| 95 | |
| 96 | // Edge Case: Game continued after a win |
| 97 | if (xWins && oCount >= xCount) { |
| 98 | throw new Error('Impossible board: game should have ended after the game was won'); |
| 99 | } |
| 100 | |
| 101 | // Edge Case: Game continued after a win |
| 102 | if (oWins && xCount > oCount) { |
| 103 | throw new Error('Impossible board: game should have ended after the game was won'); |
| 104 | } |
| 105 | |
| 106 | // Determine game state |
| 107 | if (xWins || oWins) { |
| 108 | return 'win'; |
| 109 | } |
| 110 | |
| 111 | // Edge Case: Board is full with no winner (draw) |
| 112 | if (xCount + oCount === 9) { |
| 113 | return 'draw'; |
| 114 | } |
| 115 | |
| 116 | // Edge Case: Game is still in progress |
| 117 | return 'ongoing'; |
| 12 | 118 | }; |
| 119 | |
| 120 | // Handled Edge Cases: |
| 121 | // 1. Invalid turn order - O started the game |
| 122 | // 2. Invalid turn order - X went twice in a row |
| 123 | // 3. Game continued after a win (X wins but O makes another move) |
| 124 | // 4. Game continued after a win (O wins but X makes another move) |
| 125 | // 5. Both players win (impossible scenario) |
| 126 | // 6. Board is full with no winner (draw) |
| 127 | // 7. Game is still in progress |
| 128 | // 8. Invalid board structure (not 3x3) |
| 129 | // 9. Invalid characters on board |