Thread: Help for a sudoku Solver

  1. #1
    Registered User
    Join Date
    Nov 2007

    Help for a sudoku Solver

    I am building a program that can read a sudoku game from file solve it then save it to another file.
    The problem is that I can't save the solved sudoku to file altough I have tried.
    My code is below...

    /*Sudoku Solver 
    #include <stdlib.h>
    #include <stdio.h>
    #include <string.h>
    /* S=3 for standard 9x9 sudoku, I need to find a way to determine the size of the sudoku by reading the input file*/
    #define S 2
    #define N (S*S)
    /*  last not included loop*/
    #define loop(_I,_From,_To) for (_I=_From;_I<_To;_I++)
    /*   last included loop */
    #define loopto(_I,_From,_To) for (_I=_From;_I<=_To;_I++)
    #define Error(X) do { fprintf(stderr,"ERROR %s\n",X); exit(1); } while(0)
    typedef signed char sudoku_t[N][N];
    int valid(int x,int y,int k,sudoku_t s)
    /* returns 1 if char k can be put to s[x][y] */
      int i,j,x0,y0;
      loop (i,0,N) if (s[i][y]==k) return 0;
      loop (j,0,N) if (s[x][j]==k) return 0;
      loop (i,x0,x0+S)
        loop (j,y0,y0+S) if (s[i][j]==k) return 0;
      return 1;
    void line(char *s)
    /* 1 grid line */
      int i;
      loop (i,0,N)
    void prints(sudoku_t s, char *filename)
    /* print sudoku s here is the problem.. need to save solved sudoku to a file  */
    	/* File pointers to the input file and the outputfile */
        FILE *fp;
      int x,y;
    printf("Saving %s...", filename);
    	// sanity check - game file has to exist and be writable.
    if ((fp = fopen(filename,"w")) == NULL) {
    		printf("Output file cannot be written!\n");
    		return 0;
      loop (x,0,N) {
        line(x%S?"| ":"+-");
        loop (y,0,N)
          fprintf(fp,"%c %c ",
    	     y%S?' ':'|',
    	     s[x][y]?s[x][y]<=9?s[x][y]+'0':s[x][y]+'@':' '); // here is the problem I think... :/
        fputs("|",fp); } 
       // write end of line
            fprintf(fp, "\n");
        /* Close the output file */
        fclose (fp);
    int nsol=0;
    void recursive_search(sudoku_t s)
      scans sudoku for an empty field and tries to put a number 1..N there
      if successfull, calls recursive_search again. h me8odos pou edeikses me xrisi omos ths memcpy 
      int x,y,k;
      loop (x,0,N) loop (y,0,N) {
        if (s[x][y]==0) {
          loopto (k,1,N) if (valid(x,y,k,s)) {
    	/* s[x][y]=k is valid, so let's do it and try next */
    	sudoku_t news;
    	recursive_search(news); }
          /* no digit fits s[x][y], so giving up... */
          return; } }
      /* none of s[x][y] is empty ==> we have a solution */
      nsol++; // psaxnw kai gia allo solution an yparxei ;)
    int main(int argc,char **arg)
      FILE *fp;
      sudoku_t s;
      int x,y;
      char line[128];
      if (argc<2) {
        fprintf(stderr,"No file given!");
        return 0;
      else fp=fopen(arg[1],"rt");
      if (!fp) Error(arg[1]);
      loop (x,0,N) {
        if (!fgets(line,128,fp)) Error("unexpected EOF");
        loop (y,0,N) {
          s[x][y]=line[y]==' '?0:line[y]<='9'?line[y]-'0':line[y]-'@'; 
          if (s[x][y]<0 || s[x][y]>N) Error("input"); } }
      printf("%d solution%s found\n",nsol,"s"+(nsol==1));
      return 0;

  2. #2
    Fear the Reaper...
    Join Date
    Aug 2005
    Toronto, Ontario, Canada
    That line that seems to be wrong seems awfully cluttered. Ever try unpacking it a little. Maybe then something will spring up...
    Teacher: "You connect with Internet Explorer, but what is your browser? You know, Yahoo, Webcrawler...?" It's great to see the educational system moving in the right direction

  3. #3
    Kernel hacker
    Join Date
    Jul 2007
    Farncombe, Surrey, England
    /*  last not included loop*/
    #define loop(_I,_From,_To) for (_I=_From;_I<_To;_I++)
    It generally isn't a good idea to do this.

    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  4. #4
    and the hat of int overfl Salem's Avatar
    Join Date
    Aug 2001
    The edge of the known universe
    > here is the problem I think...
    Yes, you've been overly cryptic for no good reason.

    So ultimately, all you've managed to do is out smart yourself, and now you're stuck.

    Try working on the problem and producing some readable code with meaningful variable names, and not something which you can submit to IOCCC.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

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