HDU 2896 病毒侵袭(AC自动机)

来源：互联网发布：万德软件科技有限公司编辑：程序博客网时间：2024/05/18 03:32

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;}

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