Thread: printf statements effecting program

I wrote a function that takes in a string and prints out all permutations of that string. it does this by generating random strings using the characters in the original string, and if this string is unique, it will keep it. otherwise it generates a new random string

while debugging i had some printfs in there. here is one

Code:

   char guess[strlen(string)+1];
   char permutations[numOfPermutations][strlen(string)+1];
...
         } else {
            printf("%s != %s %d\n", guess, permutations[i], i);
         }

commenting out that statement breaks the program and I dont understand why. printfs are not meant to have side effects in a program. yet somehow this one does.

this has happened to me before and I'd like to know the cause of it. it may be a beginner problem, i havent been programming for that long

I can post more/all of the code if needed

Can u paste the whole function dude

sure

anything in uppercase would be a #define'd constant

Code:

int main (void) {

   srand(time(0));

   testUnique();

   permutation ("abc");

   return EXIT_SUCCESS;

}

int allUnique(char *string) {

   int length = strlen(string);
   int i,j;
   for (i=0; i<length;i++) {
      for (j=i+1; j<length;j++) {
         if (string[i] == string[j]) {
            return 1;
         }
      }
   }
   return 0;

}


void permutation (char *string) {

   int length = strlen(string);
   int prime = 1;
   int numOfPermutations = 1;
   int i, j=0;
   int random;
   char guess[length+1];
   int same;

   for (i=length; i>0; i--) {
      numOfPermutations *= i;
   }

   char permutations[numOfPermutations][length+1];
   int upTo = 0;

   strcpy(permutations[upTo], string);
   upTo++;

   int index;

   while (upTo != numOfPermutations) {
      index = 0;

      while (index<length) {
         random = rand() % length;
         guess[index] = string[random];
         index++;
      }
      same = FALSE;
      for (i=0; i<upTo && same == FALSE; i++) {

         if (strcmp(guess, permutations[i]) == 0 ) {
            same = TRUE;
            i = upTo;

         } else {
            printf("first  %s != %s %d\n", guess, permutations[i], i);
          /*************
           problem here
           ************/
         }

      }


      if (same == FALSE && allUnique(guess) == 0) {
         // this indicates that the break condition for the previous for loop
         // was i<upTo, that is, we found a unique string
         printf("string %s is unique\n", guess);
         strcpy (permutations[upTo], guess);
         upTo++;

      } else if (strcmp (guess, "abc") == 0 && prime%ABC!=0) {

         printf("second %s\n", guess);

          /*************
           problem here
            ************/

      }



   }

   printf("showing all permutations\n");

   for (i=0; i<numOfPermutations; i++) {
      printf("%s\n", permutations[i]);
   }

}