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Added backtracking (sudoku) #205

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Merged
itsvinayak merged 2 commits into from
Jun 26, 2020
Merged

Added backtracking (sudoku) #205

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16a4658
Added backtracking (sudoku)
ruppysuppy Jun 25, 2020
868d3b6
Coverted into class based program
ruppysuppy Jun 26, 2020
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97 changes: 97 additions & 0 deletions back-tracking/Sudoku.js
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Original file line number Diff line number Diff line change
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class Sudoku {
// Sudoku Class to hold the board and related functions
constructor (board) {
this.board = board
}

findEmptyCell () {
// Find a empty cell in the board (returns [-1, -1] if all cells are filled)
for (let i = 0; i < 9; i++) {
for (let j = 0; j < 9; j++) {
if (this.board[i][j] === 0) return [i, j]
}
}
return [-1, -1]
}

check ([y, x], value) {
// checks if the value to be added in the board is an acceptable value for the cell

// checking through the row
for (let i = 0; i < 9; i++) {
if (this.board[i][x] === value) return false
}
// checking through the column
for (let i = 0; i < 9; i++) {
if (this.board[y][i] === value) return false
}

// checking through the 3x3 block of the cell
const secRow = Math.floor(y / 3)
const secCol = Math.floor(x / 3)
for (let i = (secRow * 3); i < ((secRow * 3) + 3); i++) {
for (let j = (secCol * 3); j < ((secCol * 3) + 3); j++) {
if (y !== i && x !== j && this.board[i][j] === value) return false
}
}

return true
}

solve () {
const [y, x] = this.findEmptyCell()

// checking if the board is complete
if (y === -1 && x === -1) return true

for (let val = 1; val < 10; val++) {
if (this.check([y, x], val)) {
this.board[y][x] = val
if (this.solve()) return true
// backtracking if the board cannot be solved using current configuration
this.board[y][x] = 0
}
}
// returning false the board cannot be solved using current configuration
return false
}

getSection (row, [start, end]) {
return this.board[row].slice(start, end)
}

printBoard () {
// helper function to display board
for (let i = 0; i < 9; i++) {
if (i % 3 === 0 && i !== 0) console.log('- - - - - - - - - - - -')
console.log(
...this.getSection(i, [0, 3]), ' | ',
...this.getSection(i, [3, 6]), ' | ',
...this.getSection(i, [6, 9]))
}
}
}

function main () {
// main function with an example
const sudokuBoard = new Sudoku([
[3, 0, 6, 5, 0, 8, 4, 0, 0],
[5, 2, 0, 0, 0, 0, 0, 0, 0],
[0, 8, 7, 0, 0, 0, 0, 3, 1],
[0, 0, 3, 0, 1, 0, 0, 8, 0],
[9, 0, 0, 8, 6, 3, 0, 0, 5],
[0, 5, 0, 0, 9, 0, 6, 0, 0],
[1, 3, 0, 0, 0, 0, 2, 5, 0],
[0, 0, 0, 0, 0, 0, 0, 7, 4],
[0, 0, 5, 2, 0, 6, 3, 0, 0]
])

sudokuBoard.printBoard()

console.log('\n')
sudokuBoard.solve()

sudokuBoard.printBoard()
}

main()