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    • 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>