LZ78 compression
A substitutional compression scheme which works by entering phrases into a dictionary and then, when a reoccurrence of that particular phrase is found, outputting the dictionary index instead of the phrase. Several algorithms are based on this principle, differing mainly in the manner in which they manage the dictionary.
The most well-known Lempel-Ziv scheme is Terry Welch's Lempel-Ziv Welch variant of LZ78.
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