Introducing hash tables

As we know, arrays and lists store the data elements in sequence. As in an array, the data items are accessed by an index number. Accessing array elements using index numbers is fast. However, they are very inconvenient to use when it is required to access any element when we can’t remember the index number. For example, if we wish to extract the phone number for a person from the address book at index 56, there is nothing to link a particular contact with number 56. It is difficult to retrieve an entry from the list using the index value.

Hash tables are a data structure better suited to this kind of problem. A hash table is a data structure where elements are accessed by a keyword rather than an index number, unlike in lists and arrays. In this data structure, the data items are stored in key-value pairs similar to dictionaries. A hash table uses a hashing function in order to find an index position where an element should be stored and retrieved...