HDU 2896 病毒侵袭(AC自动机)

解题思路：

对AC自动机算法的理解和应用，要注意的是，题目中的字符是128个ASCII码，而不是常用的26个英文字符，因此子节点的数目为128.

#include <iostream>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <vector>
#include <queue>
#include <string.h>
#include <stack>
#include <algorithm>
using namespace std;
struct Trie
{
    int next[210*500][128],fail[210*500],end[210*500];
    int root,L;
    int newnode()
    {
        for(int i = 0;i < 128;i++)
            next[L][i] = -1;
        end[L++] = -1;
        return L-1;
    }
    void init()
    {
        L = 0;
        root = newnode();
    }
    void insert(char buf[], int id)
    {
        int len = strlen(buf);
        int now = root;
        for(int i = 0;i < len;i++)
        {
            if(next[now][buf[i]] == -1)
                next[now][buf[i]] = newnode();
            now = next[now][buf[i]];
        }
        end[now] = id;
    }
    void build()
    {
        queue<int>Q;
        fail[root] = root;
        for(int i = 0;i < 128;i++)
            if(next[root][i] == -1)
                next[root][i] = root;
            else
            {
                fail[next[root][i]] = root;
                Q.push(next[root][i]);
            }
        while( !Q.empty() )
        {
            int now = Q.front();
            Q.pop();
            for(int i = 0;i < 128;i++)
                if(next[now][i] == -1)
                    next[now][i] = next[fail[now]][i];
                else
                {
                    fail[next[now][i]]=next[fail[now]][i];
                    Q.push(next[now][i]);
                }
        }
    }
    int vis[510];
    int query(char buf[],int n, int id)
    {
        int len = strlen(buf);
        int now = root;
        int flag = 0;
        memset(vis, 0, sizeof(vis));
        for(int i = 0;i < len;i++)
        {
            now = next[now][buf[i]];
            int temp = now;
            while( temp != root )
            {
                if(end[temp] != -1)
                {
                    vis[end[temp]] = 1;
                    flag = 1;
                }
                temp = fail[temp];
            }
        }
        if(!flag) return 0;
        printf("web %d:", id);
        for(int i=1;i<=n;i++) if(vis[i])
            printf(" %d", i);
        printf("\n");
        return 1;
    }
};
char buf[10010];
Trie ac;
int main()
{
    int n, m;
    while(scanf("%d", &n)!=EOF)
    {
        ac.init();
        for(int i=1;i<=n;i++)
        {
            scanf("%s", buf);
            ac.insert(buf, i);
        }
        ac.build();
        int ans = 0;
        scanf("%d", &m);
        for(int i=1;i<=m;i++)
        {
            scanf("%s", buf);
            if(ac.query(buf, n, i))
                ans++;
        }
        printf("total: %d\n", ans);
    }
    return 0;
}