SudokuSolver2.0

gistfile1.txt

var board = [
  [4, 5, '.', 8, '.', '.', 9, '.', '.'],
  ['.', 9, '.', '.', 5, 6, '.', '.', 4],
  [1, '.', '.', '.', '.', '.', '.', '.', 7],
  [2, 6, '.', 5, 4, '.', '.', 9, '.'],
  ['.', '.', 4, 1, '.', 2, 3, '.', '.'],
  ['.', 7, '.', '.', 6, 9, '.', 4, 8],
  [7, '.', '.', '.', '.', '.', '.', '.', 9],
  [8, '.', '.', 4, 9, '.', '.', 7, '.'],
  ['.', '.', 9, '.', '.', 3, '.', 2, 5],
]

const subgridUsedNumbers = (rowStartIndex, columnStartIndex, gameBoard) => {
  let usedNumbers = [];
  rowStartIndex *= 3;
  columnStartIndex *= 3;

  for (let i = rowStartIndex; i < rowStartIndex + 3; i++) {
    for (let x = columnStartIndex; x < columnStartIndex + 3; x++) {
      if (gameBoard[i][x] !== '.') {
        usedNumbers.push(gameBoard[i][x]);
      };
    };
  };
  return usedNumbers;  
};

const rowUsedNumbers = (rowIndex, gameBoard) => {
  let usedNumbers = [];
  for (let x = 0; x < 9; x++) {
    if (gameBoard[rowIndex][x] !== '.') {
      usedNumbers.push(gameBoard[rowIndex][x]);
    };
  };
  return usedNumbers;
};

const columnUsedNumbers = (columnIndex, gameBoard) => {
  let usedNumbers = [];
  for (let x = 0; x < 9; x++) {
    if (gameBoard[x][columnIndex] !== '.') {
      usedNumbers.push(gameBoard[x][columnIndex]);
    };
  };
  return usedNumbers;
};

const sudokuMagician = (gameBoard) => {
  for (let i = 0; i < 9; i++) {
    for (let x = 0; x < 9; x++) {
      if (gameBoard[i][x] === '.') {
        let usedGridNumbers = subgridUsedNumbers(Math.floor(i/3), Math.floor(x/3), gameBoard);
        let usedRowNumbers = rowUsedNumbers(i, gameBoard);
        let usedColumnNumbers = columnUsedNumbers(x, gameBoard);
        let combinedNumbers = [].concat(usedGridNumbers, usedRowNumbers, usedColumnNumbers)
        
        for (let y = 1; y <= 9; y++) {
          let yFound = combinedNumbers.indexOf(y);

          if (yFound < 0) {
            gameBoard[i][x] = y;
            if (sudokuMagician(gameBoard)) {
              return true;
            } else {
              gameBoard[i][x] = '.';
            };

          };
        };
        return false;
      };
    };
  };
  return true;
};
          
          
sudokuMagician(board);
console.log(board);