ABSTRACT
A computational problem species a relation between two sets of nite sequences (or two sets of strings).
Recall that a nite sequence is a nite ordered list of elements from a set. For example, an integer is a nite sequence of digits (so that 921,233,456,181 is a sequence of length 15 as written, but the commas could be omitted, which would make it a sequence of length 12). An English word is a nite sequence of letters. An array of integers can be considered a nite sequence of integers-this is the usual interpretation in an algorithms analysis class-or as a nite sequence of digits with separators.
