kmp java implement--转

http://cs.nyu.edu/~yap/classes/basic/progs/patternMatching/KMP.java

/**  * @file    KMP.java  * @synopsis     An implementation of KMP matching, derived from  *        a modification of the Match.java program.  *        Again, the goal is to find an occurrence of a pattern P in a text T.  *        CONVENTION:  *        The first index (i=0) of arrays are not used.  *  * @author    Chee Yap  * @date    Apr 25, 2001 (for Basic Algorithms class)  */public class KMP {  // Members:    char[] T;    // This is the text     char[] P;    // This is pattern    int [] fail;    // Failure function for pattern  // Constructors:    KMP(char[] p, char[] t) {      P = p; T = t;      computeFail();    } //  // Methods:    /******************************************************     Routine to compute the failure function      ******************************************************/    public void computeFail() {      // init:        fail = new int[P.length];        fail[1] = 0;      // loop:        for (int k=2; k< fail.length; k++) {          int kk = fail[k-1];          while (kk>0 && (P[kk] != P[k-1]))            kk = fail[kk];          fail[k] = 1 + kk;        }    } // computeFail(P)    /******************************************************     THIS IS THE MAIN ROUTINE     ******************************************************/    public int find(int start) {      // init:        int j = start; // text index         int k = 1; // pattern index      // loop:        while (j < T.length) {          if (k >= P.length) return(j - k + 1);          if ((T[j] == P[k]) || (k==0)) {            j++; k++;          } else {            k = fail[k];    // k could become 0          }        } // while      // Not found:        return(-1);    } // find()    /******************************************************     prints data     ******************************************************/    void output() {      System.out.print("> Pattern = \"");       for (int i=1; i< P.length; i++)         System.out.print(P[i]);      System.out.print("\"\n> Text    = \"");       for (int i=1; i< T.length; i++)         System.out.print(T[i]);      System.out.println("\"");    } // output()    /******************************************************     Main method     ******************************************************/    public static void main( String[] args) {      // sample input with 6 keys      //    (the first is a dummy key)      // char[] p = {'0', 'o', 'u'};      char[] p = {'0', 'y', 'o', 'u'};      char[] t = {'0',        'a', 'r', 'e', ' ', 'y', 'o', 'u', ' ',        'a', ' ', 'y', 'o', 'u', 't', 'h', '?'};      // construct a KMP object      KMP m = new KMP(p, t);      m.output();      // print data      // find all matches      int f = m.find(1);      if (f<1)          System.out.println(">>  No match found");      else {        while (f>=1) {          System.out.println(">>  Match found at position " + f);          f = m.find(f+1);        }//while      }//else      } // main}//class KMP