### Question 20.29

What is hashing?

Hashing is the process of mapping strings to integers, usually in a relatively small range. A ``hash function'' maps a string (or some other data structure) to a a bounded number (the ``hash bucket'') which can more easily be used as an index in an array, or for performing repeated comparisons. (Obviously, a mapping from a potentially huge set of strings to a small set of integers will not be unique. Any algorithm using hashing therefore has to deal with the possibility of ``collisions.'') Many hashing functions and related algorithms have been developed; a full treatment is beyond the scope of this list.

References: K&R2 Sec. 6.6
Knuth Sec. 6.4 pp. 506-549 Volume 3
Sedgewick Sec. 16 pp. 231-244

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