C语言中实现KMP算法的实例讲解

 int  Index(char  s[],  char  p[],  int  pos) 
 {  
  int  i,  j,  slen,  plen;  
  i  =  pos;  
  j  =  0;  
  slen  =  strlen(s);  
  plen  =  strlen(p);  
  while((i  <  slen)  &&  (j  <  plen))  
  {  
   if((s[i]  ==  p[j]))  
   {  
    i++;  
    j++;  
   }  
   else  
   {  
    i  =  i-j+1;  
    j  =  0;    
   }  
  }  
  if(j  >=  plen)  
  {  
   return  (i-plen);  
  }  
  else  
  {  
   return  -1;  
  }  
 }  

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

#define MAX 101


void get_next( int *next,char *a,int la) /*求NEXT[]的值*/
{
   int i=1,j=0 ;
   next[1] = 0 ;
   
   while ( i <= la) /*核心部分*/
   {
      if( a[i] == a[j] || j == 0 )
      {
        j ++ ;
        i ++ ;
        if( a[i] == a[j])
        next[i] = next[j];
        else
        next[i] = j ;
      }
      else
      j = next[j] ;
   }
}

int str_kmp( int *next, char *A ,char *a, int lA,int la)/* EASY*/
{
   int i,j,k ;
   i = 1 ;
   j = 1 ;
   while ( i<=lA && j <= la )
   {
      if(A[i] == a[j] || j == 0 )
      {
          i ++ ;
          j ++ ;
      }
      else
      j = next[j] ;
   }
   
   if ( j> la)
   return i-j+1 ;
   else
   return -1 ;
}

int main(void)
{
  int n,k;
  int next[MAX]={0} ;
  int lA=0,la =0 ;
  char A[MAX],a[MAX] ;
  scanf("%s %s",A,a) ;
  
  lA = strlen(A);
  la = strlen(a);
  for(k=la-1; k>= 0 ;k --)
  a[k+1] = a[k] ;
  for(k=lA-1; k>= 0 ;k --)
  A[k+1] = A[k] ;
  
  get_next(next,a,la) ;
  k = str_kmp(next,A,a,lA,la);
  if ( -1 == k)
  printf("Not Soulation!!! ");
  else
  printf("%d ",k) ;
  system("pause");
  
  return 0 ;
}