AC自动机模板 hdu2222

来源：互联网发布：java 图片文字合成编辑：程序博客网时间：2024/06/08 19:43
题目大意：
给你很多个单词，然后给你一篇文章，问给出的单词在文章中出现的次数。
#include<iostream>#include<cstdio>#include<cstring>#include<string>using namespace std;#define N 500010char str[1000010], keyword[51];int head, tail;struct node{    node *fail;    node *next[26];    int count;    node() //init    {        fail = NULL;        count = 0;        for(int i = 0; i < 26; ++i)            next[i] = NULL;    }}*q[N];node *root;void insert(char *str) //建立Trie{    int temp, len;    node *p = root;    len = strlen(str);    for(int i = 0; i < len; ++i)    {        temp = str[i] - 'a';        if(p->next[temp] == NULL)            p->next[temp] = new node();        p = p->next[temp];    }    p->count++;}void build_ac() //初始化fail指针，BFS{    q[tail++] = root;    while(head != tail)    {        node *p = q[head++]; //弹出队头        node *temp = NULL;        for(int i = 0; i < 26; ++i)        {            if(p->next[i] != NULL)            {                if(p == root) //第一个元素fail必指向根                    p->next[i]->fail = root;                else                {                    temp = p->fail; //失败指针                    while(temp != NULL) //2种情况结束：匹配为空or找到匹配                    {                        if(temp->next[i] != NULL) //找到匹配                        {                            p->next[i]->fail = temp->next[i];                            break;                        }                        temp = temp->fail;                    }                    if(temp == NULL) //为空则从头匹配                        p->next[i]->fail = root;                }                q[tail++] = p->next[i]; //入队            }        }    }}int query() //扫描{    int index, len, result;    node *p = root; //Tire入口    result = 0;    len = strlen(str);    for(int i = 0; i < len; ++i)    {        index = str[i] - 'a';        while(p->next[index] == NULL && p != root) //跳转失败指针            p = p->fail;        p = p->next[index];        if(p == NULL)            p = root;        node *temp = p; //p不动，temp计算后缀串        while(temp != root && temp->count != -1)        {            result += temp->count;            temp->count = -1;            temp = temp->fail;        }    }    return result;}int main(){    int ncase, num;    scanf("%d", &ncase);    while(ncase--)    {        head= tail = 0;        root = new node();        scanf("%d", &num);        getchar();        for(int i = 0; i < num; ++i)        {            gets(keyword);            insert(keyword);        }        build_ac();        scanf("%s", str);        printf("%d\n", query());    }    return 0;}
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