hdu 3065 病毒侵袭持续中(AC自动机)

题目链接：hdu 3065 病毒侵袭持续中

题目大意：略。

解题思路：先建立AC自动机，然后在AC自动机中开一个数组，用来记录说每个不读特征码出现的次数。

#include <cstdio>
#include <cstring>
#include <queue>
#include <vector>
#include <iostream>
#include <algorithm>

using namespace std;

typedef long long ll;

const int maxn = 50005;
const int sigma_size = 256;

struct Aho_Corasick {
    int sz, g[maxn][sigma_size];
    int tag[maxn], fail[maxn], last[maxn];
    int cnt[1005];

    void init();
    int idx(char ch);
    void insert(char* str, int k);
    void getFail();
    void match(char* str);
    void put(int u);
}A;

int N;
char s[1005][55], str[2000005];

int main () {
    while (scanf("%d", &N) == 1) {
        A.init();
        for (int i = 1; i <= N; i++) {
            scanf("%s", s[i]);
            A.insert(s[i], i);
        }
        A.getFail();

        scanf("%s", str);
        A.match(str);
        for (int i = 1; i <= N; i++)
            if (A.cnt[i])
                printf("%s: %d\n", s[i], A.cnt[i]);
    }
    return 0;
}

void Aho_Corasick::init() {
    sz = 1;
    tag[0] = 0;
    memset(g[0], 0, sizeof(g[0]));
}

int Aho_Corasick::idx(char ch) {
    return ch;
}

void Aho_Corasick::put(int u) {
    cnt[tag[u]]++;
    if (last[u])
        put(last[u]);
}

void Aho_Corasick::insert(char* str, int k) {
    int u = 0, n = strlen(str);

    for (int i = 0; i < n; i++) {
        int v = idx(str[i]);
        if (g[u][v] == 0) {
            tag[sz] = 0;
            memset(g[sz], 0, sizeof(g[sz]));
            g[u][v] = sz++;
        }
        u = g[u][v];
    }
    tag[u] = k;
}

void Aho_Corasick::match(char* str) {
    memset(cnt, 0, sizeof(cnt));

    int n = strlen(str), u = 0;
    for (int i = 0; i < n; i++) {
        int v = idx(str[i]);
        while (u && g[u][v] == 0)
            u = fail[u];

        u = g[u][v];

        if (tag[u])
            put(u);
        else if (last[u])
            put(last[u]);
    }
}

void Aho_Corasick::getFail() {
    queue<int> que;

    for (int i  = 0; i < sigma_size; i++) {
        int u = g[0][i];
        if (u) {
            fail[u] = last[u] = 0;
            que.push(u);
        }
    }

    while (!que.empty()) {
        int r = que.front();
        que.pop();

        for (int i = 0; i < sigma_size; i++) {
            int u = g[r][i];

            if (u == 0) {
                g[r][i] = g[fail[r]][i];
                continue;
            }

            que.push(u);
            int v = fail[r];
            while (v && g[v][i] == 0)
                v = fail[v];

            fail[u] = g[v][i];
            last[u] = tag[fail[u]] ? fail[u] : last[fail[u]];
        }
    }
}