Thread: My search function of a Linked List termintes mid-program!

JUst a side note, when I say 'terminate', I mean it will quit unexpectedly, I'm running in Windows atm.

1. for(i=0;i<21;i++)
You run off the end of your array

2. if(z->x == query)
Use strcmp()

3. Your formatting sucks.

Edited my search function to this:

Code:

 search(char *query,List *z) {
             int i = 1;
             printf("pass");
     while( z!= NULL ) {
            i = strcmp(query,z->x) ;
            if (i = 0) {
                  printf("yay");
                  }
                    
                    z = z->next;
                    }
                    return 0 ;                  
                    }

Still quits

I get the feeling that its this part of the code which causes it to quit

Code:

 while( z!= NULL ) {
            i = strcmp(query,z->x) ;

> if (i = 0)
Out of one pan, and into another
Use ==

Better yet, get a compiler to warn you when you do use = when you mean ==

Yeah thanks for that, it still crashes though.

Code:

typedef struct N {
  char x[20];              
  struct 	N *next;
}
List;

List *insertlist(char word[15],List *b) { // why 15 ?
  int i;
  List *c = calloc(1,sizeof(List));
  for(i=0;i<21;i++) {  // should be 20
    c->x[i] = word[i]; 
  }
  c->next = b;
  return c;
}

Code:

int main(int argc, char *argv[]) {
    char word[15];

Kurt

Changed all the 15's to 20's, but it still hangs.

Watch the !! birdies....

Code:

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

typedef struct N {
    char      x[20];
    struct N *next;
} List;

List *insertlist(char word[15], List * b)
{
    List *c = calloc(1, sizeof(List));
    strcpy( c->x, word ); /*!! use strcpy for simplicity */
    c->next = b;
    return c;
}

/*!! unused function */
List *text(char *word)
{
    List *d = NULL;
    d = insertlist(word, d);
    return d;
}

int search(char *query, List * z)   /*!! be explicit about return types */
{
    printf("pass");
    while (z != NULL) {
        if ( strcmp(z->x,query) == 0 ) {
            printf("match");
        }
        z = z->next;
    }
    return 0;
}

int main(int argc, char *argv[])
{
    char word[15];
    char query[15];
    int   x;        /*!! must be int to compare with EOF */
    List *z = NULL; /*!! an empty list */
    int c;
    FILE *fp;

    fp = fopen(argv[1], "r");
    /* set things up first - get first character, set c=0 */
    c = 0;
    while ( (x = fgetc(fp)) != EOF) {
        if (isspace(x) || ispunct(x)) {
            word[c] = '\0';
            /*for testing only - prints out each word */
            printf("%s\n", word);
            /*next char goes to start of word */
            c = 0;
            z = insertlist(word, z);
        } else {
            word[c] = x;
            /*next char goes on end of word */
            c = c + 1;
        }
    }

    fclose(fp);
    printf("Please enter a search query:");
    fgets(query, 15, stdin);
    printf("Scanned query\n");
    search(query, z);
    return 0;   /*!! needs a return result */
}

Thanks for that, how come it does not print 'match' though if I search for a word that is in the document?

Gee, do I have to do the whole thing for you?

How about trying to debug it a bit yourself - I stopped the thing crashing on you, all you have to do is dig a bit and figure it out.

Hint.

Code:

int search(char *query, List * z)
{
  printf("pass\n");
  while (z != NULL) {
    printf( "Comparing '%s' with '%s'\n", query, z->x );
    if ( strcmp(z->x,query) == 0 ) {
      printf("match\n");
    }
    z = z->next;
  }
  return 0;
}

Really big hint - read up on what fgets() stores and then read the FAQ