AC自动机

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这里有一篇很好的文章---AC自动机详解

简要介绍一下AC自动机原理：

提前你应掌握的知识：

1、字典树---Trie-Tree

2、自动机一些简单入门级概念，如（状态)

3、KMP算法的next数组的生成原理

原理如下：

1、首先由模式串构建一颗字典树 2、根据KMP中next数组的原理，构建字典树Fail指针的前缀 3、输入主串，搜索

看了以后一下是我的详细代码：

[cpp] view plaincopyprint?

<pre class="cpp" name="code">//////////////////////////////////////////////////////////////////////////
// AC自动机模板
// Author:chenzulong
// Date: 2012年3月10日
//////////////////////////////////////////////////////////////////////////
#include<iostream>
#include<algorithm>
#include<functional>
#include<queue>
#include<string>
#include<cstring>
#include<exception>
#include<typeinfo>
#include<iterator>
#ifndef AC_AUTOMAT
#define AC_AUTOMAT
class ACtomat{
//some interfaces
public:
ACtomat(){
}
~ACtomat(){
delete root;
}
//initiliation the actomat
bool ActomatInit(){
try{
index = 0;
root = &Table[index];
memset(Table[0].next,0,sizeof(Table[0].next));
Table[0].cnt = 0;
Table[0].prefix = NULL;
}catch(...){
std::cerr<<"Unknow Erro happen"<<std::endl;
return false;
}
return true;
}
//input the str-pattern ,then conostruct the trie-tree
bool insert(const std::string& str){
Trie* r = root;
std::string::const_iterator iter = str.begin();
try{
while(iter!=str.end()){
int t = *iter -'a';
if(!r->next[t]){
index++;
memset(Table[index].next,0,sizeof(Table[index].next));
Table[index].prefix = NULL;
Table[index].cnt = 0;
r->next[t] = &Table[index];
}
r = r->next[t];
iter++;
}
r->cnt++;
}catch(...){
std::cerr<<"Unknow Error happen"<<std::endl;
delete r;
r= 0;
return false;
}
//constructor the fail-pointer
if(ACtomatInitPrefix()){
return true;
}else{
return false;
}
}
//run the actomat
bool ACtomatRun(const std::string& str,int& ans){
Trie* p = root;
Trie* tp = NULL;
ans = 0;
std::string::const_iterator iter = str.begin();
try{
while(iter!=str.end()){
int t = *iter -'a';
//recurisive
while(!p->next[t]&&p!=root){
p = p ->prefix;
}
p = p->next[t];
if(!p){
p = root;
}
tp = p;
//go on matching,continue...
while(tp!=root&&tp->cnt!=-1){
ans +=tp->cnt;
tp->cnt = -1;
tp = tp->prefix;
}
iter++;
}
}catch(...){
std::cerr<<"Unknow Error happend"<<std::endl;
delete p;
delete tp;
return false;
}
return true;
}
//some constant variables
private:
enum{
MAXN_WORD=1000001,
MAXN_TOTAL = 500000
};
struct Trie{
enum{
MAXNT_NODE = 26
};
int cnt;
Trie* next[MAXNT_NODE];
Trie* prefix;
};
//some private variable
private:
Trie* root;
Trie Table[MAXN_TOTAL];
int index;
//some functions whichs are used in class
private:
//get the fail-pointer table
bool ACtomatInitPrefix(){
Trie* r,*tmp,*father;
try{
r = root;
std::queue<Trie*> q;
q.push(root);
root->prefix = NULL;
while(!q.empty()){
father = q.front();
q.pop();
for(int i=0;i<26;i++){
if(father->next[i]){
tmp = father->prefix;
while(tmp&&!tmp->next[i]){
tmp = tmp->prefix;
}
if(!tmp){
father->next[i]->prefix = root;
}else{
father->next[i]->prefix = tmp->next[i];
}
q.push(father->next[i]);
}
}
}
}catch(...){
std::cerr<<"Unkonw Error happen"<<std::endl;
delete father;
delete r;
returnfalse;
}
//delete father;
//delete r;
return true;
}
};
#endif
int main(){
int nCase;
int num;
std::string str;
std::cin>>nCase;
ACtomat* acMachine = new ACtomat;
while(nCase--){
std::cin>>num;
acMachine->ActomatInit();
while(num--){
std::cin>>str;
acMachine->insert(str);
}
std::cin>>str;
int ans ;
acMachine->ACtomatRun(str,ans);
std::cout<<ans<<std::endl;
}
return 0;
}
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