Case study4

WHAT IS HASH COLLISION?
            A hash collision, and is it really a concern for data safety in a system like Permabit Enterprise Archive.
            collision or clash is a situation that occurs when two distinct pieces of data have the same hash value, checksum, fingerprint, or cryptographic digest.
            Collisions are unavoidable whenever members of a very large set (such as all possible person names, or all possible computer files are mapped to a relatively short bit string. This is merely an instance of the pigeonhole principle.

WHAT REALLY HAPPENS DURING HASH COLLISION?

            A hash table or hash map is a data structure that uses a hash function to map identifying values, known as keys (e.g., a person's name), to their associated values (e.g., their telephone number). Thus, a hash table implements an associative array. The hash function is used to transform the key into the index (the hash) of an array element (the slot or bucket) where the corresponding value is to be sought.

Hash Table
Type	unsorted dictionary
Invented	1953

	Average	Worst case
Space	O(n)[1]	O(n)
Search	O(1 + n/k)	O(n)
Insert	O(1)	O(1)
Delete	O(1 + n/k)	O(n)