Thread: Duplicate at Hash Table

Hi, I'm running in a little trouble here. I have a hash functions which hashes a string into a hash table that is linked via linked list. It seems to produce duplicates in my node. Here are pieces of the code :

I have a fixed length record of 20 chars read from a file, I placed 21 because of the "\n". After running a strlen to count, my output is as follows :

Code:

Output:

Length : 0 0
Length : 21 0
Length : 42 21
Length : 42 21

Seems that it manage to sneak another record into my first variable. I can't figure out what's wrong.

Code:

typedef struct Bucket
{
  /* Extra node for chaining (Not relevant) */
  OverflowBucket* head;

  char record1[21];
  char record2[21];

  struct Bucket* next;
}Bucket;

/* Hash Table */
typedef struct Hashtable
{
  Bucket* head;
}HashTable;


/* This is something to simplify you guys to generate the table of 0,1,2 string keys*/
HashTable* generateTable(HashTable* table)
{
  int counter = 4;

  Bucket *bucket, *currBucket;

  while(counter != 0)
  {

    bucket = malloc(sizeof(Bucket));
    if(bucket == NULL)
    {
      fprintf(stderr,"Malloc bucket failed\n");
      exit(1);
    }
    bucket->next = NULL;

    if(table->head == NULL)
    {
      table->head = bucket;
      currBucket = bucket;
    }
    else
    {
      currBucket->next = bucket;
    }
    counter--;
  }

  return table;
}

int hash(char* buffer)
{
  int h = 0, a = 127;

  for(;*buffer != '\0'; buffer++)
    h = (a*h + *buffer) % 3;

  return h;
}

void hashToTable(char* buffer,HashTable* table)
{
  int key,count;
  Bucket *currBucket;

  currBucket = table->head;

  key = hash(buffer);

  count = key;

  /* if string key is 0 */
  if(key == 0)
  {
    if(strlen(currBucket->record1) == 0)
      strcpy(currBucket->record1,buffer);
    else if(strlen(currBucket->record2) == 0)
      strcpy(currBucket->record2,buffer);
  }
  else
  {
    /* Get corresponding node to the string key */
    while(currBucket->next != NULL)
    {
      if(count != 0)
      {
        count--;
        currBucket = currBucket->next;
      }
      else
      {
        if(strlen(currBucket->record1) == 0)
          strcpy(currBucket->record1,buffer);
        else if(strlen(currBucket->record2) == 0)
          strcpy(currBucket->record2,buffer);
      }
    }
  }
}

I'm still unable to figure out why did a duplicate copy entered my first record. Any ideas?

This is my output in strings

Code:

Output :

Record1 : 
Timmy...............
John................

Record2 :
John................

Where it should only be

Code:

Output:

Record1 : 
Timmy...............

Record2 :
John................

Need help