kmp算法 c语言(转)

/*
 * kmp.c
 *
 *  Created on: 2012-1-5
 *      Author: admin
 */

#include <stdio.h>
#include <string.h>
int index_KMP(char *s,char *t,int pos);
void get_next(char *t,int *);

char s[10]="abcacbcba";
char t[4]="abca";
int next[4];
int pos=0;

int main()
{
    int n;
    get_next(t,next);
    n=index_KMP(s,t,pos);
    printf("%d",n);
    return 0;
}

int index_KMP(char *s,char *t,int pos)
{
    int i=pos,j=1;
    while (i<=(int)strlen(s)&&j<=(int)strlen(t))
    {
        if (j==0||s[i]==t[j-1])
        {
            i++;
            j++;
        }
        else j=next[j];
    }
    if (j>(int)strlen(t))
        return i-strlen(t)+1;
    else
        return 0;
}

void get_next(char *t,int *next)
{

    int i=1,j=0;
    next[0]=next[1]=0;
    while (i<(int)strlen(t))
    {
        if (j==0||t[i]==t[j])
        {
            i++;
            j++;
            next[i]=j;
        }
        else j=next[j];
    }

}

/**************************************************************************************/

#include<stdio.h>#include<malloc.h>#include<string.h>#include<assert.h>#include<stdlib.h>void getNext(const char * t,int * Next)//get the Next array { int k=-1; int j=0; int size=strlen(t); Next[0]=-1; while(j<size) {  if(k==-1||t[j]==t[k])//if k==-1 there are two conditions    //one is this is the first time entering the loop  {   //if t[j]==t[k] get the next[j+1] directly   k++;//the other is the end of the iteration cos k==-1;   j++;   Next[j]=k;//whatever Next[j]=k    }  else   k=Next[k]; }}int myStrstr(const char * Dest,const char *subStr)//find the starting position of the sub{                                                 //in the Dest through KMP int destSize=strlen(Dest); int subSize=strlen(subStr); int i,j; int * Next=(int *)(malloc(sizeof(int)*subSize)); i=j=0; assert((Dest!=NULL)&&(subStr!=NULL)); getNext(subStr,Next); while(i<destSize&&j<subSize) {  if(j==-1||Dest[i]==subStr[j])//if j==-1 the main string need match the next elements  {                            //and the subString begin from the beginning   i++;                     //if Dest[i]==subStr[j]  both string need shift to the   j++;                     // next elements  }  else   j=Next[j];                   //if match fail,glide back to Next[j] } if(j==subSize)return i-j; return -1;}int main(){ char *temp,*sub,* Dest;//to store the substring to be matched int ch; unsigned int templen,length=20*sizeof(char); unsigned int mlength=20*sizeof(char);//the original length of the memory sub=(char*)malloc(length); Dest=(char*)malloc(length); if(sub==NULL||Dest==NULL)//allocation failure {  printf("memory allocate failure\n");  exit(0); } temp=sub; printf("please input the substring:\n"); while((ch=getchar())!=10)//read the sub String {  if((temp-sub)/sizeof(char)==length)//if running out of the memory  {   templen=length;   sub=realloc(sub,length+=20*sizeof(char));   if(sub==NULL)   {    printf("sub memory allocate failure\n");    exit(0);   }   temp=sub+templen*sizeof(char);//reset the temp cos the sub may change its value  }  *temp++=ch; } *temp='\0'; temp=Dest; printf("please input the mainstring:\n"); while((ch=getchar())!=10)//read the main String {  if((temp-Dest)/sizeof(char)==mlength)  {   templen=mlength;   Dest=realloc(Dest,mlength+=20*sizeof(char));//if running out of the memory   if(Dest==NULL)   {    printf("sub memory allocate failure\n");    exit(0);   }   temp=Dest+templen*sizeof(char);//reset the temp cos the Dest may change its value  }  *temp++=ch; } *temp='\0'; printf("the starting position is :%d\n",myStrstr(Dest,sub));//get the starting position free(Dest); free(sub); return 0;}