HDOJ 3065 病毒侵袭持续中（AC自动机入门）

思路：

AC自动机，单词统计。

#include <iostream>
#include <deque>
using namespace std;

const int MAX_NODE = 1000 * 50 + 10;
const int CHILD_NUM = 26;

char virus[1010][56];
int num[1010];

class AcAutomaton 
{
private:
    int size;
    int trie[MAX_NODE][CHILD_NUM];
    int value[MAX_NODE];
    int fail[MAX_NODE];
    int table[128];

public:
    void Initialize()
    {
        fail[0] = 0;
        memset(table, -1, sizeof(table));
        for (int i = 0; i < 26; ++i)
            table['A' + i] = i;
    }

    void Reset()
    {
        size = 1;
        memset(trie[0], 0, sizeof(trie[0]));
        memset(fail, 0, sizeof(fail));
        memset(value, 0, sizeof(value));
    }

    void Insert(char* word, int key)
    {
        int p = 0;
        for (int i = 0; word[i]; ++i)
        {
            int m = table[word[i]];
            if (!trie[p][m])
            {
                memset(trie[size], 0, sizeof(trie[0]));
                trie[p][m] = size++;
            }
            p = trie[p][m];
        }
        value[p] = key;
    }

    void Construct()
    {
        deque<int> deq;

        for (int i = 0; i < CHILD_NUM; ++i)
            if (trie[0][i])
            {
                fail[trie[0][i]] = 0;
                deq.push_back(trie[0][i]);
            }

        while (!deq.empty())
        {
            int u = deq.front();
            deq.pop_front();
            for (int i = 0; i < CHILD_NUM; ++i)
            {
                int& v = trie[u][i];
                if (v)
                {
                    fail[v] = trie[fail[u]][i];
                    deq.push_back(v);
                }
                else
                    v = trie[fail[u]][i];
            }
        }
    }

    void Work(char* word, int arr[])
    {
        int p = 0;
        for (int i = 0; word[i]; ++i)
        {
            int m = table[word[i]]; 
            if (m == -1) 
            {
                p = 0; continue;
            }
            int t = p = trie[p][m];
            while (value[t])
            {
                ++arr[value[t]];
                t = fail[t];
            }
        }
    }
};

AcAutomaton Ac;
char word[2000010];

int main()
{
    int n;
    Ac.Initialize();
    while (~scanf("%d", &n))
    {
        Ac.Reset();

        for (int i = 1; i <= n; ++i)
        {
            scanf("%s", virus[i]);
            Ac.Insert(virus[i], i);
        }
        Ac.Construct();

        scanf("%s", word);
        memset(num, 0, sizeof(num));
        Ac.Work(word, num);

        for (int i = 1; i <= n; ++i)
            if (num[i])
                printf("%s: %d\n", virus[i], num[i]);
    }
    return 0;
}