HDU1867.cpp KMP中发生不匹配时，j=next[j],j的含义

#include<stdio.h>
#include<string.h>
#define size 100009
void getnext(char *p,int *next)
{
int i,j;
next[0]=-1;
i=0,j=-1;
int len=strlen(p);
while(i<len)
{
if(j==-1 || p[i]==p[j])i++,j++,next[i]=j;
else j=next[j];
}
}

void kmp(char *s,char *p,int *next,char *ans)
{
int i,j;
i=0,j=0;
int l1=strlen(s);
int l2=strlen(p);
if(l1>l2)
i=l1-l2;
while(i<l1 && j<l2)
{
if(j==-1 || s[i]==p[j])i++,j++;
else j=next[j];
}
strcpy(ans,s);
strcpy(ans+l1,p+j);

}
int main()
{
char s[size],t[size],ans1[size*2],ans2[size*2];
int next1[size],next2[size];
while(~scanf("%s%s",s,t))
{
getnext(s,next1);
getnext(t,next2);
kmp(s,t,next2,ans1);
kmp(t,s,next1,ans2);
int l1=strlen(ans1);
int l2=strlen(ans2);
if(l1>l2)
printf("%s\n",ans2);
else if(l1<l2)
printf("%s\n",ans1);
else if(l1==l2)
{
if(strcmp(ans1,ans2)>0)
printf("%s\n",ans2);
else printf("%s\n",ans1);
}

}
return 0;
}