sudioku

package com.company;

import java.util.*;

public class Sudoku {
    public static int[][] sudokuInDigits = new int[9][9]; //matricata kydeto se pazi sudokuto
    private static boolean solved = false;//uslovie za izlizane ot rekursiqta
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String[][] sudoku = new String[9][9];
        int placesToFill = 0;
        for (int i = 0; i < sudoku.length; i++) {
            for (int j = 0; j < 1; j++) {
                sudoku[i][j] = in.next();
                    for (int k = 0; k < 9; k++) {
                        //prevryshtane ot String kym int na vxoda
                        if (sudoku[i][k] != "-") {
                            int digit = sudoku[i][j].charAt(k) - '0';
                            if (digit > 0) {
                                sudokuInDigits[i][k] = digit;
                            }
                            else {
                                //dynoto na rekursiqta
                                placesToFill++;
                            }
                        }
                    }
            }
        }
        solveSudoku(placesToFill, 0);
        //printirane na gotovoto sudoku
        for (int i = 0; i < sudokuInDigits.length; i++) {
            for (int j = 0; j < sudokuInDigits[i].length; j++) {
                System.out.print(sudokuInDigits[i][j]);
            }
            System.out.println();
        }
    }

    private static void solveSudoku(int squaresLeft, int nextNumber) {
        if (squaresLeft == 0 || solved) {
            solved = true;
            return;
        }
        for (int i = 0; i < sudokuInDigits.length; i++) {
            for (int j = 0; j < sudokuInDigits[i].length; j++) {
                //obxojdane na matricata za da vidim kyde lipsvat chisla
                if (sudokuInDigits[i][j] == 0) {
                    for (int k = 1; k < 10; k++) {
                        //proverki za tova koe chislo lipsva i koe se sydyrja na syotvetniq red/kolona
                        //ili kvadratche
                        if (checkRow(k,i) == true && checkColumn(j,k) == true
                                && checkSquare(i,k,j) == true) {
                            sudokuInDigits[i][j] = k;
                            squaresLeft--;
                            solveSudoku(squaresLeft,k + 1);
                            //neobxodimo za da moje da kato se vryshta rekursiqta
                            //da ne promenq tekushtoto systoqnie
                            if(solved)
                                return;
                            //pri otkriti konflikti vyzstanovqvame predishnoto systoqnie
                            //na matricata
                            sudokuInDigits[i][j] = 0;
                            squaresLeft++;
                        }
                    }
                    return;
                }
            }
        }
        return;
    }

    private static boolean checkRow(int candidate, int row) {
        //proverka za reda dali sydyrjda chisloto
        for (int col = 0; col < 9; col++ ) {
            if (sudokuInDigits[row][col] == candidate)
                return false;
        }
        return true;
    }

    private static boolean checkColumn(int column, int candidate) {
        //proverka za kolonata dali sydyrja chisloto
        for (int row = 0; row < 9; row++ ) {
            if (sudokuInDigits[row][column] == candidate)
                return false;
        }
        return true;
    }

    private static boolean checkSquare(int row, int candidate, int column) {
        //izchisleniq za tova kakvo e razstoqnieto ot [0,0] do [row,column]
        int colMultiplier = column / 3;
        int rowMultiplier = row / 3;
        int cellsInASquareSide = 3;
        //proverka na kvadratcheto
        for (int i = 0; i < 9; i++) {
            if (sudokuInDigits[i % 3 + rowMultiplier * cellsInASquareSide][i / 3 +
                        colMultiplier * cellsInASquareSide] == candidate) {
                return false;
            }
        }
        return true;
    }
}