fast-sudoku-solver
Version:
A fast Sudoku solver written in TypeScript.
52 lines • 2.37 kB
JavaScript
import { cloneSudoku, getPossibleEntries, isCorrectlySolved } from './solver-utils';
/**
* Solves Sudoku puzzles. The first entry of the returned array is *false* if the Sudoku puzzle is not solvable.
* @param sudoku Sudoku puzzle to solve
* @returns solved Sudoku puzzle. The first entry of the returned array is *false* if the Sudoku puzzle is not solvable.
*/
export function solveSudokuPuzzle(sudoku) {
let minNumberOfPossibleEntries = 10; // initially set to something greather than 9 such that one field is picked even in empty Sudoku
let rowMinNumber = -1;
let columnMinNumber = -1;
let possibleEntriesMinNumber = [];
for (let i = 0; i < 9; i++) {
for (let j = 0; j < 9; j++) {
// field already filled? continue with next field
if (sudoku[i][j] >= 1) {
continue;
}
// get possible entries for current field
const possibleEntries = getPossibleEntries(sudoku, i, j);
// no possible entries? Sudoku not solvable
if (possibleEntries.length === 0) {
return [false, sudoku];
}
// only one possibility left? add entry and start recursive call
if (possibleEntries.length === 1) {
const clone = cloneSudoku(sudoku);
clone[i][j] = possibleEntries[0];
return solveSudokuPuzzle(clone);
}
// multiple possible entries? find field with lowest number of possibilities
if (possibleEntries.length < minNumberOfPossibleEntries) {
minNumberOfPossibleEntries = possibleEntries.length;
rowMinNumber = i;
columnMinNumber = j;
possibleEntriesMinNumber = possibleEntries;
}
}
}
// if arrived here: try out as many possibilities as needed for field with lowest number of possibilities
const clone = cloneSudoku(sudoku);
for (let i = 0; i < possibleEntriesMinNumber.length; i++) {
clone[rowMinNumber][columnMinNumber] = possibleEntriesMinNumber[i];
const result = solveSudokuPuzzle(clone);
if (!result[0]) {
continue;
}
return result;
}
// if arrived here: solver is done
return [isCorrectlySolved(clone), clone];
}
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