// KMP算法
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void get_next(char *T,int next[])	//修正前的next数组 
{
int i = 1,j = 0;
next[0] = -1;
next[1] = 0;
int m = strlen(T);
while(i<strlen(T)-1)
{
if(j == -1||T[j]==T[i])
{
++i;
++j;
next[i] = j;
}
else j = next[j];
}
} 

void get_nextval(char *T,int nextval[])	//修正后的nextval数组
{
int i = 1,j = 0;
nextval[0] = -1;
nextval[1] = 0;
int m = strlen(T);
while(i<strlen(T)-1)
{
if(j == -1||T[j]==T[i])
{
++i;
++j;
if(T[i]!=T[j]) nextval[i] = j;
else nextval[i] = nextval[j];
}
else j = nextval[j];
}
} 

int Index_kmp(char *S,char *T,int pos,int next[])	//逐项比较 
{
int j = 0,i = pos,lens=strlen(S),lent=strlen(T);
get_next(T,next);
while(i<lens&&j<lent)
{
if(S[i]==T[j]||j==-1)
{
i++;j++;
}
else j = next[j];
}
if(j>=lent) return i-lent;
else return -1;
}

int main()
{
char *S="adbadabbaabadabbadada",*T="adabbadada";
int m;
int *next = (int *)malloc((strlen(T)+1)*sizeof(int));	//修正前的next数组
int *nextval = (int *)malloc((strlen(T)+1)*sizeof(int));	//修正后的nextval数组

get_next(T,next);
printf("修正前next数组为：");
for(m = 0;m<strlen(T);m++)
{
printf("%d ",next[m]+1);
}

get_nextval(T,nextval);
printf("\n修正后的nextval数组为：");
for(m=0;m<strlen(T);m++)
{
printf("%d ",nextval[m]+1);
}


int t = Index_kmp(S,T,0,nextval);
if(t==-1) printf("\n无匹配项！\n");
else
{
printf("\n在第%d项开始匹配成功\n",t+1);
}
return 0;
}