Thread: bus error in code

I can't figure out why I'm getting a bus error here..

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void RecursivePermute(char jumble[], int k, char * words[], int size_of_dictionary);
void ExchangeCharacters(char jumble[], int i, int j);
int inDictionary(char jumble[], char * words[], int size_of_dictionary);

// Pre-condition: 'words' is a valid C String, and 'k' is non-negative and
//                less than or equal to the length of words.
// Post-condition: All of the permutations of words with the first 'k'
//                 characters fixed in their original positions are
//                 printed. Namely, if n is the length of words, then
//                 (n-k)! permutations are printed.
void RecursivePermute(char jumble[], int k, char * words[], int size_of_dictionary) {
	
	int i, j;
	
	// Base-case: Since all letters are fixed, we can ONLY print
	// what's stored in str.
	if (k == strlen(jumble)) {
		if(inDictionary(jumble, words, size_of_dictionary) == 1) {
			printf("A permutation of %s that is a valid word is .\n", jumble);
		}
	}
	else {
		
		// Loop through each possible starting letter for index k,
		// the first index for which we have a choice.
		for (j=k; j<strlen(jumble); j++) {
			
			// Place the character stored in index j in location k.
			ExchangeCharacters(jumble, k, j);
			
			// Print out all of the permutations with that character
			// just chosen above fixed. 
			RecursivePermute(jumble, k+1, words, size_of_dictionary);
			
			// Put the original character that used to be there back
			// in its place.
			ExchangeCharacters(jumble, j, k);
		}
	}
}

// Pre-condition: words is a valid C String and i and j are valid indexes
//                to that string.
// Post-condition: The characters at index i and j will be swapped in
//                 str.
void ExchangeCharacters(char jumble[], int i, int j) {
	
    char temp = jumble[i];
    jumble[i] = jumble[j];
    jumble[j] = temp;
}

int inDictionary(char jumble[], char * words[], int size_of_dictionary) {

	int left=0, mid, right=size_of_dictionary-1;
	
	while(left <= right) {
		mid = (left + right)/2;
		if((strcmp(jumble, words[mid])) == 0) {
			return 1;
		}
		if((strcmp(jumble, words[mid])) < 0) {
			left = mid + 1;
		}
		if((strcmp(jumble, words[mid])) > 0) {
			right = mid - 1;
		}
	}
	return 0;

}

It seems like the array named "words" is not being read into function inDictionary properly, and I know the program experiences the bus error at the moment it tries to compute the strcmp function. I've had no luck troubleshooting though..help anyone??

You should have posted the whole thing (which you did, before your edit).
All the real horrors are in the bit you removed.

Code:

int main() {

FILE * ifp;
int size_of_dictionary, num_of_jumbled_words;
int i, j;
char ** words;
char jumble;

ifp = fopen("dictionary.in", "r");
if(ifp == NULL) {
printf("The file that you are trying to access is invalid.\n");
}
else {
fscanf(ifp, "%d", &size_of_dictionary);
}

for(i=0; i<size_of_dictionary; i++) {
words = (char **)malloc(size_of_dictionary*sizeof(char*));
// Bad bad, you're allocating your outer array EVERY time
// All except the last pointer is gonna be junk

if(words == NULL) {
printf("Sorry, there is not enough available memory to be allocated.\n");
break;
}
words[i] = (char*)malloc(sizeof(char)*MAX_SIZE);
fscanf(ifp, "%s", &words[i]);
}
fclose(ifp);

ifp = fopen("jumble.txt", "r");
fscanf(ifp, "%d", &num_of_jumbled_words);

for(j=1; j<=num_of_jumbled_words; j++) {
printf("Jumble #%d:\n", j);
fscanf(ifp, "%s", &jumble);
// jumble is a char, you're reading a string

RecursivePermute(&jumble, 0, words, size_of_dictionary);
}

fclose(ifp);
free(words);
return 0;

}

Your approach sucks - happy now?
How many times do you call strlen(jumble).

> But I don't understand why that would change by just moving it out of the previous for loop as instructed.
You don't? It's worse than I thought.

Can you figure out why
if(words == NULL)
should be outside the loop as well?

> words[i] = (char*)malloc(sizeof(char)*MAX_SIZE);
Or why you SHOULD check this for NULL

> ifp = fopen("jumble.txt", "r");
And this for NULL as well.

> free(words);
You should free each words[i] before this.

> But if you read the bottom of my post
But if you read the top, the story is different.

> if(inDictionary(jumble, words, size_of_dictionary) == 1)
Strange, the function returns the INDEX of where the string is found.
Being an index, zero is also a valid result, AND is also your "not found" result as well.