text字符串中找到pat模式串。

//KMP算法

#include  <string.h>   

void setup(char pat[], int fail[])
{
     int  length = strlen(pat);
     int  i, j;

     fail[0] = -1;
     for (i = 1; i < length; i++) {
          for (j=fail[i-1]; j>=0 && pat[j+1]!=pat[i]; j=fail[j])
               ;
          fail[i] = (j < 0 && pat[j+1] != pat[i]) ? -1 : j+1;
     }
}

int KMP(char text[], char pat[], int fail[])
{
     int  t_length = strlen(text);
     int  p_length = strlen(pat);
     int  t, p;

     setup(pat, fail);        /* build up the fail func.  */
     for (t = p = 0; t < t_length && p < p_length; )
          if (text[t] != pat[p]) /* if not match …      */
               if (p > 0)     /* is it the 1st location?  */
                    p = fail[p-1] + 1; /* no, shift right */
               else
                    t++;      /* or match next in text[]  */
          else
               t++, p++;      /* matched, advance both    */
     return (p >= p_length) ? t – p_length : -1;
}

/* —————————————————— */

#include  <stdio.h>

#define   MAXSIZE  100

void main(void)
{
     char  text[MAXSIZE];
     char  pat[MAXSIZE];
     int   fail[MAXSIZE];
     int   answer, i;

     printf(“\nKnuth-Morris-Pratt String Search Program”);
     printf(“\n========================================”);
     printf(“\n\nText String ——> “);
     gets(text);
     printf(  “\nPattern String —> “);
     gets(pat);

     if ((answer = KMP(text, pat, fail)) >= 0) {
          printf(“\n “);
          for (i = 1; i <= 6; i++)
               printf(”         %1d”, i);
          printf(“\n”);
          for (i = 1; i <= 6; i++)
               printf(“0….5….”);
          printf(“0”);
          printf(“\n%s\n”, text);
          for (i = 0; i < answer; i++)
               printf(” “);
          printf(“%s”, pat);
          printf(“\n\nPattern Found at location %d”, answer);
     }
     else
          printf(“\nPattern NOT found”);
}

//BM算法

#include  <string.h>          /* for strlen()             */

#define   NOT_FOUND      -1

void  get_jump(unsigned char [], int []);
int   BM(unsigned char [], unsigned char []);

int  BM(unsigned char text[], unsigned char pat[])
{
     int  jump_tab[256];
     int  t_len = strlen(text);
     int  p_len = strlen(pat);
     int  i, j, k;

     get_jump(pat, jump_tab); /* compute the jump table   */
     for (i = p_len – 1; i < t_len; ) { /* comp. downward */
          for (j=p_len-1, k=i; j >= 0 && text[k] == pat[j]; k–,j–)
               ;
          if (j < 0)          /* if pat[] exhausted ?     */
               return k + 1;  /* YES, pattern found.      */
          else                /* NO, update using jump_tab*/
               i += jump_tab[text[i]];
     }
     return NOT_FOUND;        /* text[] exhausted.        */
}

void  get_jump(unsigned char pat[], int jump_tab[])
{
     int  length = strlen(pat);
     int  i;

     for (i = 1; i < 256; i++) /* assume length is the gap*/
          jump_tab[i] = length;
     for (i = 0; i < length – 1; i++) /* now adjust them. */
          jump_tab[(int)pat[i]] = length – i – 1;
}

/* —————————————————— */

#include  <stdio.h>
#include  <stdlib.h>

#define   MAXSIZE       100

void main(void)
{
     unsigned char  text[MAXSIZE];
     unsigned char  pat[MAXSIZE];
     int            answer, i;
    
     printf(“\nBoyer-Moore String Searching Program”);
     printf(“\n====================================”);
     printf(“\n\nText String    –> “);
     gets(text);
     printf(  “\nPattern String –> “);
     gets(pat);

     if ((answer = BM(text, pat)) >= 0) {
          printf(“\n “);
          for (i = 1; i <= 6; i++)
               printf(”         %1d”, i);
          printf(“\n”);
          for (i = 1; i <= 6; i++)
               printf(“0….5….”);
          printf(“0”);
          printf(“\n%s\n”, text);
          for (i = 0; i < answer; i++)
               printf(” “);
          printf(“%s”, pat);
          printf(“\n\nPattern Found at location %d”, answer);
     }
     else
          printf(“\nPattern NOT FOUND.”);
}