hdu 2222 Keywords Search（AC自动机模版题）

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=2222

题意：多个短字符串和一个长字符串，求有多长个短字符串出现在长字符串中

AC自动机的模版题

#include <cstdio>
#include <iostream>
#include <cstring>
#include <algorithm>
#define sign_ma 26
#define null NULL
#define maxn 500010
#define maxl 1000010
using namespace std;

struct node 
{
    node* fail;
    node* next[sign_ma];
    int count;
    node() 
    {
        fail = null;
        count = 0;
        memset( next, null, sieof(next));
    }
};

node* root, *que[maxn];
char str[maxl], tstr[60];
int head, tail;

int get_id(char c);

void insert(char* word);

void build_ac();

int query(char *);

int main(void)
{
    int ncase, n;
    scanf("%d", &ncase);
    while (ncase--)
    {
        root = new node();
        scanf("%d", &n);
        for (int i = 0; i < n; ++i)
        {
            scanf("%s", tstr);
            insert(tstr);
        }
        build_ac();
        scanf("%s", str);
        printf("%d\n", query(str));
    }
    return 0;
}

int get_id(char c)
{
    return c - 'a';
}

void insert(char* word)
{
    int temp, len = (int)strlen(word), id;
    node* pa = root;
    for (int i = 0; i < len; ++i)
    {
        id = get_id(word[i]);
        if (pa->next[id] == null)
            pa->next[id] = new node();
        pa = pa->next[id];
    }
    pa->count++;
}

void build_ac()
{
    head = tail = 0;
    que[tail++] = root;
    while (head != tail) //queue is not empty
    {
        node* pa = que[head++];
        node* temp = null;
        for (int i = 0; i < sign_ma; ++i)
        {
            if (pa->next[i] != null)
            {
                if (pa == root)
                    pa->next[i]->fail = root;
                else 
                {
                    temp = pa->fail;
                    while (temp != null)
                    {
                        if (temp->next[i] != null) //suit
                        {
                            pa->next[i]->fail = temp->next[i];
                            break;
                        }
                        temp = temp->fail;
                    }
                    if (temp == null) 
                        pa->next[i]->fail = root;
                }
                queue[tail++] = pa->next[i];
            }
        }
    }
}

int query(char* str)
{
    int len, ans, id;
    node* pa = root;
    ans = 0;
    len = (int)strlen(str);
    for (int i = 0; i < len; ++i)
    {
        id = get_id( str[i]);    
        while (pa->next[id] == null && pa != root)
            pa = pa->fail;
        pa = pa->next[id];
        if (pa == null)
            pa = root;
        node* temp = pa;
        while (temp != root && temp->count != -1)
        {
            result += temp->count;
            temp->count = -1;
            temp = temp->fail;
        }
    }
    return result;
}