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sudokuCore.js
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sudokuCore.js
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// Global Variables
const SUDOKUBOARDWIDTH = 9;
const SUDOKUINNERGRIDWIDTH = 3;
var digits = [1, 2, 3, 4, 5, 6, 7, 8, 9];
var validCellsMap = new Map();
var invalidCellsMap = new Map();
var currentDigitCellsMap = new Map();
// Classes
class SudokuBoard {
constructor() {
this.board = create2DArray();
this.unusedDigits = digits.slice();
fillMaps();
}
createNewGame() {
// Step 1: Fill up grid with numbers considering sudoku constraints
fillBoard.call(this);
console.log(this.board);
// Step 2: Remove cells considering difficulty level.
}
}
function test(){
for (let i = 0; i < 50; i++) {
var boardObj = new SudokuBoard();
boardObj.createNewGame();
}
}
function fillMaps() {
for (let i = 0; i < SUDOKUBOARDWIDTH; i++)
{
// first two maps are digits to rows with an array of cells.
validCellsMap[digits[i]] = new Array(9);
invalidCellsMap[digits[i]] = new Array(9);
// this map is [digits] to array of cells
currentDigitCellsMap[digits[i]] = []
for (let j = 0; j < SUDOKUBOARDWIDTH; j++) {
validCellsMap[digits[i]][j] = [];
invalidCellsMap[digits[i]][j] = [];
}
}
}
function fillBoard() {
// foreach digit, loop through rows
this.unusedDigits.forEach(digit => {
// For each digit you'll be able to see cells that were valid for
// each row to avoid unnecessarily re-applying constraints
// when backtracking
for (let currentRow = 0; currentRow < SUDOKUBOARDWIDTH; currentRow++) {
validCellsMap[digit][currentRow] = getValidCellsForRow.call(this, currentRow, digit);
// Check if you need to backtrack
if (!validCellsMap[digit][currentRow].length > 0) {
var isBacktrackingRequired = true;
// check if you need to go back down a digit
var backRow = currentRow - 1;
var backDigit = digit;
if(currentRow - 1 == -1){
// It will go down to 8 in the method parameter
backRow = 8;
backDigit = digit - 1;
}
while (isBacktrackingRequired) {
backTrack.call(this, backDigit, backRow);
validCellsMap[digit][currentRow] = getValidCellsForRow.call(
this,
currentRow,
digit
);
isBacktrackingRequired = !validCellsMap[digit][currentRow].length > 0;
}
}
var indexToUse = selectRandomInt(validCellsMap[digit][currentRow].length);
var cellToUse = validCellsMap[digit][currentRow][indexToUse];
this.board[cellToUse.row][cellToUse.column] = digit;
// console.log(this.board);
currentDigitCellsMap[digit].push(cellToUse);
}
});
}
function backTrack(digit, backTrackRow) {
var failedCell = currentDigitCellsMap[digit].pop();
// console.log(this.board);
// You need to unset the cell
this.board[failedCell.row][failedCell.column] = null;
invalidCellsMap[digit][backTrackRow].push(failedCell);
validCellsMap[digit][backTrackRow].pop(failedCell);
// Check if you need to backtrack
if (!validCellsMap[digit][backTrackRow].length > 0) {
var isBacktrackingRequired = true;
invalidCellsMap[digit][backTrackRow] = [];
// check if you need to go back down a digit
var backRow = backTrackRow - 1;
var backDigit = digit;
if(backTrackRow - 1 == -1){
// It will go down to 8 in the method parameter
backRow = 8;
backDigit = digit - 1;
}
while (isBacktrackingRequired) {
backTrack.call(this, backDigit, backRow);
validCellsMap[digit][backTrackRow] = getValidCellsForRow.call(
this,
backTrackRow,
digit
);
isBacktrackingRequired = !validCellsMap[digit][backTrackRow].length > 0;
}
}
var indexToUse = selectRandomInt(validCellsMap[digit][backTrackRow].length);
var cellToUse = validCellsMap[digit][backTrackRow][indexToUse];
this.board[cellToUse.row][cellToUse.column] = digit;
currentDigitCellsMap[digit].push(cellToUse);
}
function selectRandomInt(upperBound) {
return Math.floor(Math.random() * Math.floor(upperBound));
}
// function shuffle(a) {
// var j, x, i;
// for (i = a.length - 1; i > 0; i--) {
// j = Math.floor(Math.random() * (i + 1));
// x = a[i];
// a[i] = a[j];
// a[j] = x;
// }
// return a;
// }
function getValidCellsForRow(currentRow, digit) {
var rowValues = this.board[currentRow];
var cellList = [];
for (let i = 0; i < rowValues.length; i++) {
// 3rd constraint (cellsAlreadyFilledIn)
if (rowValues[i] == null) {
cellList.push({ row: currentRow, column: i });
}
}
// 1st constraint (cells used previously in higher rows)
if (currentDigitCellsMap[digit].length > 0) {
cellList = cellList.filter(isNotInSameColumnAsUsedDigitCells, digit);
// 2nd constraint (Regions of previous cells)
if (currentRow % SUDOKUINNERGRIDWIDTH > 0) {
// This row isn't a new region so this constraint will apply.
cellList = cellList.filter(isNotInSameRegionAsUsedDigitCells, digit);
}
}
// Backtrack constraint (Is not in invalid cells)
if (invalidCellsMap[digit][currentRow].length > 0) {
cellList = cellList.filter(isNotInInvalidCellsList, [currentRow, digit]);
}
return cellList;
}
function isNotInInvalidCellsList(cell) {
var currentRow = this[0];
var digit = this[1];
var isNotInInvalid = true;
if (invalidCellsMap[digit][currentRow].includes(cell)) {
isNotInInvalid = false;
}
return isNotInInvalid;
}
function isNotInSameRegionAsUsedDigitCells(cell) {
// Step 1: Get used cells in the current region [x]
// Step 2: Loop through the cells in the current region
// Step 3: Compare each cell in the current region with
// the cell you are testing.
var isNotInSameRegion = true;
var digit = this;
var currentRegionToCheck = Math.floor(currentDigitCellsMap[digit].length / SUDOKUINNERGRIDWIDTH);
var startIndexToInclude = currentRegionToCheck * SUDOKUINNERGRIDWIDTH;
var endBoundIndex = startIndexToInclude + SUDOKUINNERGRIDWIDTH;
var usedCellsInCurrentRegion = currentDigitCellsMap[digit].slice(startIndexToInclude, endBoundIndex);
for (let i = 0; i < usedCellsInCurrentRegion.length; i++) {
if (
Math.floor(currentDigitCellsMap[digit][i].column / SUDOKUINNERGRIDWIDTH) ==
Math.floor(cell.column / SUDOKUINNERGRIDWIDTH)
) {
isNotInSameRegion = false;
break;
}
}
return isNotInSameRegion;
}
function isNotInSameColumnAsUsedDigitCells(cell) {
var isNotInSameColumn = true;
var digit = this;
for (let i = 0; i < currentDigitCellsMap[digit].length; i++) {
if (currentDigitCellsMap[digit][i].column == cell.column) {
isNotInSameColumn = false;
break;
}
}
return isNotInSameColumn;
}
function create2DArray() {
// JavaScript doesn't have a built-in way of creating
// 2D arrays so you literally create an
// array of arrays.
var outerArray = new Array(SUDOKUBOARDWIDTH);
for (let i = 0; i < outerArray.length; i++) {
outerArray[i] = new Array(SUDOKUBOARDWIDTH);
}
return outerArray;
}