#include<stdio.h>
#include<stdlib.h>
#include<time.h>
int x,y;
int matrix[9][9], box[9];
char filename[30];
FILE *fp;
void welcome(void);
void rules(void);
void level(void);
void board(char);
void enter(int);
void check(int);
main()
{
      welcome();
      rules();
}
void welcome()
{
     printf("Welcome to Sudoku Game Version 2.0\n\n");
     printf("Thanks for playing this game!\n\nHope you enjoy!\n");
}
void rules()
{
     printf("\nRules to play:\n");
     printf("Enter a numerical digit from 1 through 9 starting with various digits given in some cells.\n");
     printf("Each row, column, and cell must contain only one instance of each numeral.\n");
     printf("Are you ready for the game? (1 - Yes, 0 - No)\n");
     scanf("%d", &x);
     if(x==1)
         level();
     else
         exit(1);
}
void level()
{
 printf("Which level do you want to play? (1-simple, 2-medium, 3-hard)\n");
 scanf("%d", &y);
 switch(y)
 {
  case 1:
   printf("Please choose which puzzle you want to play!\n");
   printf("Enter a no within 1-10. Add .txt after the no.\n");
   printf("Puzzle to play: (Enter no, eg. 1.txt)\n");
   scanf("%s", filename);
   board(filename);
  break;
  case 2:
   printf("Please choose which puzzle you want to play.\n");
   printf("Enter a no within 11-20. Add .txt after the no.\n");
   printf("Puzzle to play: (Enter no, eg. 11.txt)\n");
   scanf("%s", filename);
   board(filename);
  break;
  case 3:
   printf("Please choose which puzzle you want to play.\n");
   printf("Enter a no within 21-30. Add .txt after the no.\n");
   printf("Puzzle to play: (Enter no, eg. 21.txt)\n");
   board(filename);
  break;
  default:
   printf("Wrong Entering! No must be 1,2 or 3!\n");
   level();
    fclose(fp);
    }
}
void board(char filename[30])
{
 int i,j,z;
 fp=fopen(filename,"r");
    if(fp==NULL)
 {
    printf("Cannot open file!\n");
    level();
 }
    while((z=fgetc(fp))!=EOF){
 
         printf("|-|-|-|-|-|-|-|-|-|\n");
         for(i=0;i<9;i++)
         {
               for(j=0;j<=9;j++)
               {
                   z = fgetc(fp);
 
          printf("|%c",z);
 
                   matrix[i][j] = z;
 
               }                 
         }
    printf("\n");     
    printf("|-|-|-|-|-|-|-|-|-|\n");
    }    
}
void enter(int matrix[9][9])
{
     int a,b,c;
 
     printf("Enter the position that you want to enter numbers: (eg. 1,1)\n");
     scanf("%d,%d", &a,&b);
 
     if(matrix[a][b]==0)
     {
             printf("Wrong entering!\n");
             printf("Please enter the position again!\n");
             enter(matrix);
     }
 
     if(matrix[a][b]!=0)
     {
             printf("Enter the number that you want to put at the position:\n");
             scanf("%d", &c);
 
             matrix[a][b] = c;
 
             check();      
     }
}

{
    int index = 1 ;
    for( index = 1; index <= 9; ++index ) {
        if( matrix[row][index] == value_entered ) {
            if( index == col ) {
                continue ;
            }
            else {
                printf( "The value is already present" ) ;
                return 0 ; // return false, condtition not satisfied
            }
        }
    }
 
    for( index = 1; index <= 9; ++index ) {
        if( matrix[index][col] == value_entered ) {
            if( index == row ) {
                continue ;
            }
            else {
                printf( "The value is already present" ) ;
                return 0 ; // return false, condtition not satisfied
            }
        }
    }
 
    return 1 ; // value not present already, so continue adding the new value to matrix
}