Internal mechanics of a hash table

A hash table is generally an encapsulation around an array, and the basic principle on which it works is quite simple. We know that accessing a data item in an array is a constant time O(1) operation if we know the index where the data item is stored.

We can leverage an array's fast random-access property to map a key and value together. We can store the original key-value pair at that index by using a hash function that converts the given key into an array's index(hash value). A good hash function guarantees that a given key will always result in the same index, and the computation is a constant-time operation. Once we fix the index for a key, the data can be accessed in constant time in the array.