SudokuSolver

import java.util.Scanner;
public class SudokuSolver {
    public static int[][] grid = new int[10][10];
    boolean isSafe(int num,int r,int c){
    int i,j,rs,cs;
    for(i=0; i<9; i++){
        if(grid[r][i]==num){
            return false;
        }
    }
    for(i=0; i<9; i++){
        if(grid[i][c]==num){
            return false;
        }
    }
    rs=r-r%3;
    cs=c-c%3;
    for(i=0; i<3; i++){
        for(j=0; j<3; j++){
            if(grid[rs+i][cs+j]==num){
                return false;
            }
        }
    }
    return true;
    }
    boolean solve(){
        boolean flag;
        flag = false;
        int i,j = 0;
        for(i=0; i<9; i++){
           for(j=0; j<9; j++){
            if(grid[i][j]==0){
                flag=true;
                break;
            }
        }
        if(flag){
            break;
        }
    }
    int rval = i;
    int cval = j;
    if(!flag){
        return true;
    }
    else{
        for(i=1; i<=9; i++){
            if(isSafe(i,rval,cval)){
                grid[rval][cval]=i;
                if(solve()){
                    return true;
                }
                grid[rval][cval]=0;
            }
        }
    }
        return false;
    }
    public static void main(String[] args) {
     Scanner sf = new Scanner(System.in);
     SudokuSolver ob = new SudokuSolver();
     int i,j,x,val,y,cnt;
     for(i = 0; i<9;i++){
                 for(j = 0; j<9;j++){
                     grid[i][j]=0;
                 }
             }
     while(true){
         x = sf.nextInt();
         if(x == 0){
             cnt = 0;
             for(i = 0; i<9;i++){
                 for(j = 0; j<9;j++){
                     if(grid[i][j] !=0){ cnt++;}
                 }
             }
             if(cnt<18){
                 System.out.println("you should input at lest 18 number");
             }
             else break;
         }
         else {
             y = sf.nextInt(); val = sf.nextInt();
             grid[--x][--y] = val;
         }
     }
    if(ob.solve()){
        for(i=0; i<9; i++){
            for(j=0; j<9; j++){
                System.out.print(grid[i][j]+" ");
            }
            System.out.println();
        }
    }
    else{
        System.out.print("No solution exists\n");
    }
    }
}