| 1 | | // |
| 2 | | // This is only a SKELETON file for the 'State of Tic Tac Toe' exercise. It's been provided as a |
| 3 | | // convenience to get you started writing code faster. |
| 4 | | // |
| 5 | | |
| 6 | | /** |
| 7 | | * @param {string[]} board |
| 8 | | * @returns {string} |
| 1 | /* |
| 2 | * Determines the state of a Tic-Tac-Toe game based on the given board. |
| 3 | * |
| 4 | * @param {string[]} board - An array of strings representing the game board. |
| 5 | * @returns {string} - Returns 'win', 'draw', or 'ongoing' based on the game state. |
| 6 | * @throws {Error} - Throws an error for invalid board states with specific messages. |
| 9 | 7 | */ |
| 10 | 8 | export const gamestate = (board) => { |
| 11 | | throw new Error('Remove this line and implement the function'); |
| 12 | | }; |
| 9 | // Validate board dimensions |
| 10 | if (board.length !== 3 || board.some(row => row.length !== 3)) { |
| 11 | throw new Error('Invalid board: must be 3x3'); |
| 12 | } |
| 13 | |
| 14 | // Count X's and O's |
| 15 | let xCount = 0; |
| 16 | let oCount = 0; |
| 17 | |
| 18 | for (let i = 0; i < 3; i++) { |
| 19 | for (let j = 0; j < 3; j++) { |
| 20 | const cell = board[i][j]; |
| 21 | if (cell === 'X') xCount++; |
| 22 | else if (cell === 'O') oCount++; |
| 23 | else if (cell !== ' ') { |
| 24 | // Edge Case: Invalid characters on the board |
| 25 | throw new Error('Invalid board: contains invalid characters'); |
| 26 | } |
| 27 | } |
| 28 | } |
| 29 | |
| 30 | // Edge Case: Wrong turn order - O started (O has marks when X should have started) |
| 31 | if (xCount === 0 && oCount > 0) { |
| 32 | throw new Error('Wrong turn order: O started'); |
| 33 | } |
| 34 | |
| 35 | // Edge Case: Wrong turn order - X went twice (X has more than 1 extra mark) |
| 36 | if (xCount > oCount + 1) { |
| 37 | throw new Error('Wrong turn order: X went twice'); |
| 38 | } |
| 39 | |
| 40 | // Edge Case: Wrong turn order - O went twice (O has more marks than X but game not over) |
| 41 | // We'll check this after win detection to allow valid final states |
| 42 | |
| 43 | // Check for wins |
| 44 | const winPatterns = [ |
| 45 | // Rows |
| 46 | [[0,0], [0,1], [0,2]], |
| 47 | [[1,0], [1,1], [1,2]], |
| 48 | [[2,0], [2,1], [2,2]], |
| 49 | // Columns |
| 50 | [[0,0], [1,0], [2,0]], |
| 51 | [[0,1], [1,1], [2,1]], |
| 52 | [[0,2], [1,2], [2,2]], |
| 53 | // Diagonals |
| 54 | [[0,0], [1,1], [2,2]], |
| 55 | [[0,2], [1,1], [2,0]] |
| 56 | ]; |
| 57 | |
| 58 | let xWins = false; |
| 59 | let oWins = false; |
| 60 | |
| 61 | for (const pattern of winPatterns) { |
| 62 | const [a, b, c] = pattern; |
| 63 | const valA = board[a[0]][a[1]]; |
| 64 | const valB = board[b[0]][b[1]]; |
| 65 | const valC = board[c[0]][c[1]]; |
| 66 | |
| 67 | if (valA !== ' ' && valA === valB && valB === valC) { |
| 68 | if (valA === 'X') xWins = true; |
| 69 | else if (valA === 'O') oWins = true; |
| 70 | } |
| 71 | } |
| 72 | |
| 73 | // Edge Case: Both players win (impossible in valid game) |
| 74 | if (xWins && oWins) { |
| 75 | throw new Error('Impossible board: game should have ended after the game was won'); |
| 76 | } |
| 77 | |
| 78 | // Edge Case: Game continued after win - only check when there's a clear violation |
| 79 | // When X wins, O should not have more marks than X |
| 80 | if (xWins && oCount > xCount) { |
| 81 | throw new Error('Impossible board: game should have ended after the game was won'); |
| 82 | } |
| 83 | |
| 84 | // When O wins, X should not have more marks than O |
| 85 | if (oWins && xCount > oCount) { |
| 86 | throw new Error('Impossible board: game should have ended after the game was won'); |
| 87 | } |
| 88 | |
| 89 | // Edge Case: Wrong turn order - O went twice (O has more marks than X in ongoing game) |
| 90 | // Only check this for ongoing games, not for completed games (win/draw) |
| 91 | const isBoardFull = (xCount + oCount === 9); |
| 92 | const isGameOngoing = !xWins && !oWins && !isBoardFull; |
| 93 | |
| 94 | if (isGameOngoing && oCount > xCount) { |
| 95 | throw new Error('Wrong turn order: O went twice'); |
| 96 | } |
| 97 | |
| 98 | // Determine game state |
| 99 | if (xWins || oWins) { |
| 100 | return 'win'; |
| 101 | } |
| 102 | |
| 103 | // Edge Case: Board is full (draw) |
| 104 | if (xCount + oCount === 9) { |
| 105 | return 'draw'; |
| 106 | } |
| 107 | |
| 108 | // Edge Case: Game is not finished yet |
| 109 | return 'ongoing'; |
| 110 | |
| 111 | // Handled Edge Cases: |
| 112 | // - Invalid characters on the board |
| 113 | // - Wrong turn order (O started) |
| 114 | // - Wrong turn order (X went twice) |
| 115 | // - Both players win (impossible) |
| 116 | // - Game continued after win (X won but O played) |
| 117 | // - Game continued after win (O won but X played) |
| 118 | // - Board is full (draw) |
| 119 | // - Game is not finished yet (ongoing) |
| 120 | }; |