字符串匹配 KMP算法

from Introduction to Algorithm

KMP-MATCHER(T,P)

n = T.length m = P.length pi = COMPUTE-PREFIX-FUNCTION(P) for i = 1 to n while q>0 and P[q+1] != T[i] q = pi[q] if P[q+1] == T[i]  q = q + 1  if q == m  print " Pattern occurs with shift" i-m  q = pi[q]

COMPUTE-PREFIX-FUNCTION(P)

m = P.length let pi[m] be a new array pi[1] = 0 k = 0 for q = 2 to m  while k > 0 && P[k+1] != P[q]  k = pi[q]  if P[k+1] == P[q]  k = k + 1  pi[q] = k return pi

i.e

let P = "ababbabbabbababbabb"

then pi = [0, 0, 1, 2, 0, 1, 2, 0, 1, 2, 0, 1, 2, 3, 4, 5, 6, 7, 8]