HDU 2896 病毒侵袭（AC自动机）-优快云博客

本文链接：https://blog.youkuaiyun.com/watermuch/article/details/9673907

本文通过一道具体的模板题，详细介绍了AC自动机的构建过程及其应用。从建立字典树开始，逐步讲解如何进行节点匹配及失败指针的设置，并最终实现字符串查询的功能。文章深入浅出地解释了AC自动机的原理，对于理解该算法并解决相关问题非常有帮助。

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这题模板题.............但是竟然要去重........调试了半天才发现....................

#include <cstdio>
#include <iostream>
#include <cstring>
#include <cmath>
#include <algorithm>
using namespace std;

struct trie {
    trie *next[128];
    int flag;
    int num;
    trie *fail;
    trie() {
        fail = NULL;
        flag = num = 0;
        memset(next,0,sizeof(next));
    }
}*q[511111];

trie *rt = new trie();
int vi[555],cnt,head,tail;
char keyword[222];
char book[11111];

void insert(char *key,int num) {
    trie *p = rt;
    while(*key) {
        int t = int(*key);
        if(p->next[t] == NULL) p->next[t] = new trie();
        p = p->next[t];
        key ++;
    }
    p->flag = 1;
    p->num = num;
}

void bfs() {
    rt->fail = NULL;
    head = tail = 0;
    q[head++] = rt;
    while(head != tail) {
        trie *t = q[tail++];
        trie *tmp = NULL;
        for(int i=0; i<128; i++) {
            if(t->next[i] != NULL) {
                if(t == rt ) t->next[i]->fail = rt;
                else {
                    tmp = t->fail; //沿着父亲的fail指针走
                    while(tmp != NULL) {
                        if(tmp->next[i] != NULL) {
                            t->next[i]->fail = tmp->next[i];
                            break;
                        }
                        tmp = tmp->fail;
                    }
                    if(tmp == NULL) t->next[i]->fail = rt;
                }
                q[head++] = t->next[i];
            }
        }
    }
}


void query(char *key) {
    trie *p = rt;
    cnt = 0;
    int ok = 0;
    while(*key) {
        int t = int(*key);
        while(p != rt && p->next[t] == NULL) p = p->fail;
        p = p->next[t];
        if(p == NULL) p = rt;
        trie *tmp = p;
        while(tmp != rt && tmp->flag != 0) {
            vi[cnt] = tmp->num;
            cnt += tmp->flag;
            tmp = tmp->fail;
        }
        key++;
    }
}
int main() {
    int n,m;
    cin >> n;
    getchar();
    for(int i=0; i<n; i++) {
        gets(keyword);
        insert(keyword,i+1);
    }
    bfs();
    int ans = 0;
    cin >> m;
    getchar();
    for(int i=1; i<=m; i++) {
        gets(book);
        memset(vi,0,sizeof(vi));
        cnt = 0;
        query(book);
        if(cnt != 0) {
            ans ++;
            printf("web %d:",i);
            sort(vi,vi+cnt);
            int dd = unique(vi , vi + cnt) - vi;
            for(int j=0; j<dd; j++) printf(" %d",vi[j]);
            puts("");
        }
    }
    printf("total: %d\n",ans);
    return 0;
}