hashindeks

A hash index, also known as a hash table or hash map, is a data structure that implements an associative array abstract data type, a structure that can map keys to values. The primary idea behind a hash index is to use a hash function to compute an index, also called a hash code, into an array of buckets or slots. This allows for very fast average-case time complexity for lookup, insertion, and deletion operations, often approaching O(1).

The hash function takes a key as input and returns an integer value. This integer is then typically mapped to an index within the bounds of the array. For example, if the array has 100 slots, the hash function's output might be taken modulo 100 to determine the slot. When a key-value pair needs to be stored, the key is hashed to find the appropriate slot, and the pair is stored there. When retrieving a value, the key is hashed again to find its location, and the corresponding value is returned.

A critical challenge with hash indexes is handling collisions, which occur when two different keys hash to the same index. Various collision resolution strategies exist, such as separate chaining (where each bucket stores a linked list of entries) or open addressing (where if a slot is occupied, the algorithm probes for another slot). The efficiency of a hash index depends heavily on the quality of the hash function and the chosen collision resolution method. A good hash function distributes keys evenly across the array, minimizing collisions.