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| 1 | +class Sudoku { |
| 2 | + // Sudoku Class to hold the board and related functions |
| 3 | + constructor (board) { |
| 4 | + this.board = board |
| 5 | + } |
| 6 | + |
| 7 | + findEmptyCell () { |
| 8 | + // Find a empty cell in the board (returns [-1, -1] if all cells are filled) |
| 9 | + for (let i = 0; i < 9; i++) { |
| 10 | + for (let j = 0; j < 9; j++) { |
| 11 | + if (this.board[i][j] === 0) return [i, j] |
| 12 | + } |
| 13 | + } |
| 14 | + return [-1, -1] |
| 15 | + } |
| 16 | + |
| 17 | + check ([y, x], value) { |
| 18 | + // checks if the value to be added in the board is an acceptable value for the cell |
| 19 | + |
| 20 | + // checking through the row |
| 21 | + for (let i = 0; i < 9; i++) { |
| 22 | + if (this.board[i][x] === value) return false |
| 23 | + } |
| 24 | + // checking through the column |
| 25 | + for (let i = 0; i < 9; i++) { |
| 26 | + if (this.board[y][i] === value) return false |
| 27 | + } |
| 28 | + |
| 29 | + // checking through the 3x3 block of the cell |
| 30 | + const secRow = Math.floor(y / 3) |
| 31 | + const secCol = Math.floor(x / 3) |
| 32 | + for (let i = (secRow * 3); i < ((secRow * 3) + 3); i++) { |
| 33 | + for (let j = (secCol * 3); j < ((secCol * 3) + 3); j++) { |
| 34 | + if (y !== i && x !== j && this.board[i][j] === value) return false |
| 35 | + } |
| 36 | + } |
| 37 | + |
| 38 | + return true |
| 39 | + } |
| 40 | + |
| 41 | + solve () { |
| 42 | + const [y, x] = this.findEmptyCell() |
| 43 | + |
| 44 | + // checking if the board is complete |
| 45 | + if (y === -1 && x === -1) return true |
| 46 | + |
| 47 | + for (let val = 1; val < 10; val++) { |
| 48 | + if (this.check([y, x], val)) { |
| 49 | + this.board[y][x] = val |
| 50 | + if (this.solve()) return true |
| 51 | + // backtracking if the board cannot be solved using current configuration |
| 52 | + this.board[y][x] = 0 |
| 53 | + } |
| 54 | + } |
| 55 | + // returning false the board cannot be solved using current configuration |
| 56 | + return false |
| 57 | + } |
| 58 | + |
| 59 | + getSection (row, [start, end]) { |
| 60 | + return this.board[row].slice(start, end) |
| 61 | + } |
| 62 | + |
| 63 | + printBoard () { |
| 64 | + // helper function to display board |
| 65 | + for (let i = 0; i < 9; i++) { |
| 66 | + if (i % 3 === 0 && i !== 0) console.log('- - - - - - - - - - - -') |
| 67 | + console.log( |
| 68 | + ...this.getSection(i, [0, 3]), ' | ', |
| 69 | + ...this.getSection(i, [3, 6]), ' | ', |
| 70 | + ...this.getSection(i, [6, 9])) |
| 71 | + } |
| 72 | + } |
| 73 | +} |
| 74 | + |
| 75 | +function main () { |
| 76 | + // main function with an example |
| 77 | + const sudokuBoard = new Sudoku([ |
| 78 | + [3, 0, 6, 5, 0, 8, 4, 0, 0], |
| 79 | + [5, 2, 0, 0, 0, 0, 0, 0, 0], |
| 80 | + [0, 8, 7, 0, 0, 0, 0, 3, 1], |
| 81 | + [0, 0, 3, 0, 1, 0, 0, 8, 0], |
| 82 | + [9, 0, 0, 8, 6, 3, 0, 0, 5], |
| 83 | + [0, 5, 0, 0, 9, 0, 6, 0, 0], |
| 84 | + [1, 3, 0, 0, 0, 0, 2, 5, 0], |
| 85 | + [0, 0, 0, 0, 0, 0, 0, 7, 4], |
| 86 | + [0, 0, 5, 2, 0, 6, 3, 0, 0] |
| 87 | + ]) |
| 88 | + |
| 89 | + sudokuBoard.printBoard() |
| 90 | + |
| 91 | + console.log('\n') |
| 92 | + sudokuBoard.solve() |
| 93 | + |
| 94 | + sudokuBoard.printBoard() |
| 95 | +} |
| 96 | + |
| 97 | +main() |
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