• Thomas Graf's avatar
    [LIB]: Knuth-Morris-Pratt textsearch algorithm · df3fb93a
    Thomas Graf authored
    Implements a linear-time string-matching algorithm due to Knuth,
    Morris, and Pratt [1]. Their algorithm avoids the explicit
    computation of the transition function DELTA altogether. Its
    matching time is O(n), for n being length(text), using just an
    auxiliary function PI[1..m], for m being length(pattern),
    precomputed from the pattern in time O(m). The array PI allows
    the transition function DELTA to be computed efficiently
    "on the fly" as needed. Roughly speaking, for any state
    "q" = 0,1,...,m and any character "a" in SIGMA, the value
    PI["q"] contains the information that is independent of "a" and
    is needed to compute DELTA("q", "a") [2]. Since the array PI
    has only m entries, whereas DELTA has O(m|SIGMA|) entries, we
    save a factor of |SIGMA| in the preprocessing time by computing
    PI rather than DELTA.
    [1] Cormen, Leiserson, Rivest, Stein
        Introdcution to Algorithms, 2nd Edition, MIT Press
    [2] See finite automation theory
    Signed-off-by: default avatarThomas Graf <tgraf@suug.ch>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Makefile 1.34 KB