Efficient string matching in the presence of errors

Consider the string matching problem where differences between characters of the pattern and characters of the text are allowed. Each difference is due to either a mismatch between a character of the text and a character of the pattern or a superfluous character in the text or a superfluous character in the pattern. Given a text of length n, a pattern of length m and an integer k, we present an algorithm for finding all occurrences of the pattern in the text, each with at most k differences. The algorithm runs in O(m2 + k2n) time. Given the same input we also present an algorithm for finding all occurrences of the pattern in the text, each with at most k mismatches (superfluous characters in either the text or the pattern are not allowed). This algorithm runs in O(k(m logm + n)) time.