How does a hash table work?

Question

I\'m looking for an explanation of how a hash table works - in plain English for a simpleton like me!

For example, I know it takes the key, calculates the hash (I a

Answer 1

For all those looking for programming parlance, here is how it works. Internal implementation of advanced hashtables has many intricacies and optimisations for storage allocation/deallocation and search, but top-level idea will be very much the same.

(void) addValue : (object) value
{
   int bucket = calculate_bucket_from_val(value);
   if (bucket) 
   {
       //do nothing, just overwrite
   }
   else   //create bucket
   {
      create_extra_space_for_bucket();
   }
   put_value_into_bucket(bucket,value);
}

(bool) exists : (object) value
{
   int bucket = calculate_bucket_from_val(value);
   return bucket;
}

where calculate_bucket_from_val() is the hashing function where all the uniqueness magic must happen.

The rule of thumb is: For a given value to be inserted, bucket must be UNIQUE & DERIVABLE FROM THE VALUE that it is supposed to STORE.

Bucket is any space where the values are stored - for here I have kept it int as an array index, but it maybe a memory location as well.