利用有限自动机进行字符串匹配

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

int maxPrefix(const char* str1, const char* str2);

int
state_transport(const char* p, const int n, const int m, char a)
{
  char pk[n+2];
  strncpy(pk, p, n);
  pk[n]=a;
  pk[n+1]='\0';
  return maxPrefix(pk, p);
}

int
maxPrefix(const char* str1, const char* str2)
{
  int len1=strlen(str1);
  int len2=strlen(str2);
  int i , j, k;
  int count = 0;
  int maxCount=0;
  int l = len1 > len2 ? len2:len1;
  for(i=1; i<=l; ++i){
    for(k=len1-i, j=0;k<len1 && j<len2; ++k, ++j){
      if(str1[k]==str2[j]){
	count++;
      }
      else{
	count = 0;
	break;
      }
    }
    if(count > maxCount) maxCount=count;
    count = 0;
  }
  return maxCount;
}

int
matchCount(const char* t, const char* sub_str, int m)
{
  int len = strlen(t);
  int q = 0;
  for(int i = 0; i < len; ++i){
    q = state_transport(sub_str, q, m, t[i]);
    if(q == m){
      printf("occur in %d\n", i+1-m);
    }
  }
}

int
main()
{
  const char* str1="abcababababab";
  const char* str2="abab";
  matchCount(str1, str2, 4);
}