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#include <conio.h>
#include <iostream>
using namespace std;
//aabaad
//aaaad
//00110
void getNext(const char* P,int next[])
{
int m=strlen(P);
next[0]=0;
cout<<P<<endl;
for(int i=1;i<m; i++)
{
int j=next[i-1];
getch();
cout<<"比较Pi["<<i<<"]="<<P[i]<<",Pj["<<j<<"]="<<P[j]<<endl;
while(j>0&&P[i]!=P[j])
{
j=next[j-1];
cout<<"j=next[j-1]="<<j<<",j的值变为"<<j<<endl;
}
if(P[i]==P[j])
{
next[i]=j+1;
cout<<"两者相等:"<<"next[i "<<i<<" ]=j+1;"<<j+1<<",j="<<j<<endl;
}
else
{
next[i]=0;
cout<<"两者不等:"<<"next[i "<<i<<" ]=0;"<<endl;
}
cout<<"最后:next["<<i<<"]="<<next[i]<<endl;
}
cout<<"next 的排列为:"<<endl;
for(int i=0;i<m; i++)
{
cout<<next[i]<<" ";
}
cout<<endl;
}
int KMP(char* s,char* t,int next[])
{
int iSlen=strlen(s);
int iTlen=strlen(t);
int i = 0;
int j = 0;
cout<<s<<endl;
cout<<t<<endl;
while (i < iSlen && j < iTlen)
{
getch();
cout<<"第"<<i<<"个数据是"<<s[i]<<", 第"<<j<<"个数据是"<<t[j]<<endl;
if (s[i] == t[j])
{
i++;
j++;
cout<<"准备比较下一组数据:"<<"i="<<i<<",j="<<j<<endl;
}
else
{
if (j == 0)//如果s[i]与t[0]不等,那么直接比较下一个
{
i++;
}
else//如果s[i]与t[j]不等,那么回退到上一个可以继续比较的结点,继续匹配
{
int iTmp=j;
j = next[j];
if (j==0)
{
i=i-iTmp+1;
}
}
cout<<"两者不等,J取最近的一个值"<<",j="<<j<<", 准备比较下一组数据:"<<"i="<<i<<",j="<<j<<endl;
}
cout<<&s[i]<<endl;
cout<<&t[j]<<endl;
}
if (j == iTlen)
return i-j;
return -1;
}
int main(void)
{
char *s = "adsfaababababababababababababababdababababab", *t = "abababdabab";
int iSlen=strlen(s);
int iTlen=strlen(t);
int* next=new int[iTlen];
getNext(t,next);
int i= KMP(s,t,next);
delete[] next;
cout<<i;
cout<<"正确答案"<<strstr(s,t)-s;
getch();
system("pause");
return 0;
}
#include<iostream>
#include<cstring>
using namespace std;
int *GetNext(char *t){
int tlen=strlen(t);
int *next=new int[tlen];
if(!next)
return 0;
next[0]=-1;
int i=0,j=next[i];
while(i<tlen){
if(j==-1 || t[i]==t[j]){
i++;
j++;
next[i]=j;
}
else
j=next[j];
}
return next;
}
int StrIndex_KMP(char *s,char *t,int pos){
//从串s下标为pos开始找首次与串t相等的子串,next数组中为next函数的相关值
int *next=GetNext(t);
int slen,tlen;
slen=strlen(s);
tlen=strlen(t);
int i,j;
i=pos; j=0;
while(i<slen && j<tlen){ //没遇到结束符
if(j==-1 || s[i]==t[j]){
i++;
j++;
}
else
j=next[j];//右滑
}
delete []next;
next=NULL;
if(j==tlen)
return i-tlen;//匹配成功,返回子串首字符的下标
else
return -1;//匹配失败返回-1
}
int main(){
char s[1000],t[1000];
while(cin>>s>>t){
if(StrIndex_KMP(s,t,0)==-1)
cout<<"匹配失败"<<endl;
else
cout<<StrIndex_KMP(s,t,0)<<endl; //输出匹配的下标
}
return 0;
}
int iTmp=j;
j = next[j];
if (j==0)
{
i=i-iTmp+1;
}