LempelZivalgoritmit

LempelZivalgoritmit, often referred to as LZ algorithms, is a family of lossless data compression algorithms. These algorithms were developed by Abraham Lempel and Jacob Ziv in the late 1970s. The core idea behind LZ algorithms is to replace repeated occurrences of data within a file with references to a single occurrence of that data. This is achieved by building a dictionary of sequences encountered so far. When a sequence is seen again, it is replaced by a pointer to its previous occurrence in the dictionary, along with its length.

There are several variations of the LZ algorithm, with LZ77 and LZ78 being the foundational ones. LZ77 works by looking back into a sliding window of recently processed data. If a match is found, it's encoded as a (distance, length) pair. LZ78, on the other hand, builds an explicit dictionary of phrases encountered. When a new phrase is encountered, it's added to the dictionary, and the encoder outputs a code representing the longest prefix of the current input that is already in the dictionary.

These algorithms form the basis for many widely used compression formats such as ZIP, GZIP, and PNG. Their effectiveness lies in their ability to exploit redundancy in data, making them suitable for a broad range of file types, including text, executable files, and images. While modern compression techniques often build upon the principles of Lempel and Ziv, their original work revolutionized the field of data compression.