http://acm.hdu.edu.cn/showproblem.php?pid=2222&&AC自動機

第一道AC自動機題~ 其實就是字典樹上的KMP演算法，主要就是學會建字典樹和構造失敗指標。字典樹我用的是數組類比的方法~

AC代碼：

#include <iostream>#include<string.h>#include<algorithm>#include<cstdio>#include<queue>#define Fp freopen("1.txt","r",stdin)#define N 2000005using namespace std;void in(int &a){    char ch;    while((ch=getchar())<'0'||ch>'9');    for( a=0;ch>='0'&&ch<='9';ch=getchar()) a=a*10+ch-'0';}typedef struct node{int next[26];int num;int fail;void init(){memset(next,-1,sizeof(next));num=0;fail=-1;}}Node;Node s[N];int p;char a[1000000];void insert(){int ind=0;for(int i=0;a[i];++i){int x=a[i]-'a';if(s[ind].next[x]==-1) {     s[++p].init();     s[ind].next[x]=p;     }ind=s[ind].next[x];}++s[ind].num;}void AC(){queue<int>Q;int root=0;s[root].fail=-1;Q.push(root);while(!Q.empty()){int t=Q.front();Q.pop();for(int i=0;i<26;++i){int ind=s[t].next[i];if(ind!=-1){if(t==root) s[ind].fail=root;else{  int p=s[t].fail;  while(p!=-1)  {  if(s[p].next[i]!=-1)  {  s[ind].fail=s[p].next[i];  break;  }  p=s[p].fail;  }  if(p==-1) s[ind].fail=root;  }Q.push(ind);}    }}}int  Find(){    int root=0;     int ct=0;    int res=root;    for(int i=0;a[i];++i)    {        int x=a[i]-'a';        while(res!=root&&s[res].next[x]==-1) res=s[res].fail;        res=s[res].next[x];        if(res==-1) res=root;        int ans=res;        while(ans!=root&&s[ans].num>0)        {            ct+=s[ans].num;            s[ans].num=-1;            ans=s[ans].fail;       }    }    return ct;}int main(){   Fp;   int T;   in(T);   while(T--)   {       s[0].init();       int n;       //scanf("%d",&n);       in(n);       //gets(a);       while(n--)       {           gets(a);           insert();       }       gets(a);       AC();       printf("%d\n",Find());   }return 0;}

參考：

http://blog.csdn.net/niushuai666/article/details/7002823

http://www.cnblogs.com/zhuangli/archive/2008/08/13/1267249.html