7: Hash Tables
A hash table , or a hash map , is a data structure that associates keys with values . The primary operation it supports efficiently is a lookup : given a key (e.g. a person's name), find the corresponding value (e.g. that person's telephone number). It works by transforming the key using a hash function into a hash , a number that the hash table uses to locate the desired value. This hash maps directly to a bucket in the array of key/value pairs, hence the name hash map. The mapping method lets us directly access the storage location for any key/value pair.
Hash table<Element> Operations
make-hash-table(integer n ): HashTable
- Create a hash table with n buckets.
get-value(HashTable h , Comparable key ): Element
- Returns the value of the element for the given key . The key must be some comparable type.
set-value(HashTable h , Comparable key , Element new-value )
- Sets the element of the array for the given key to be equal to new-value . The key must be some comparable type.
remove(HashTable h , Comparable key )
- Remove the element for the given key from the hash table. The key must be some comparable type.