AC自动机

知识点详解

hdu 2222

#include 
#include 
#include 
#include 
#include 
using namespace std;

const int N = 1e6+10;

struct node{
    int count;              //是否为该单词的最后一个节点
    node *next[26];         //Tire每个节点的26个子节点（最多26个字母）
    node *fail;             //失败指针
    node() {                //构造函数初始化
    	fail = NULL;
    	count = 0;
    	memset(next, NULL, sizeof(next));
    }
}*q[500001];                //队列，方便用于bfs构造失败指针
char keyword[55];           //输入的单词
char str[N];                //模式串
int head, tail;             //队列的头尾指针

void insert(char *str, node *root) {
	int i = 0;
	node *p = root;
	while(str[i]) {
		int index = str[i] - 'a';
		if(p -> next[index] == NULL) p->next[index] = new node;
		p = p->next[index];
		i++;
	}
	p->count++;
}

void build_ac_automation(node *root) {
	root -> fail = NULL;
	q[head++] = root;
	while(head != tail) {
		node *temp = q[tail++];
		node *p = NULL;
		for(int i = 0; i < 26; i++) {
			if(temp->next[i] == NULL) continue;
			if(temp == root) temp->next[i]->fail = root;
			else {
				p = temp->fail;
				while(p!=NULL) {
					if(p->next[i] != NULL) {
						temp->next[i]->fail = p->next[i];
						break;
					}
					p = p->fail;
				} 
				if(p == NULL) temp->next[i]->fail = root;
			}
			q[head++] = temp->next[i];
		}
	}
}

int query(char *str, node *root) {
	int i = 0;
	int cnt = 0;
	node *p = root;
	while(str[i]) {
		int index = str[i] - 'a';
		while(p->next[index]==NULL && p!=root) p = p->fail;
		p = p->next[index];
		p = (p==NULL)?root:p;
		node *temp = p;
		while(temp!=root && temp->count!=-1) {
			cnt += temp->count;
			temp->count = -1;
			temp = temp->fail;
		}
		i++;
	}
	return cnt;
}

int main() {
	int T;
	scanf("%d", &T);
	while(T--) {
		node *root = new node();
		head = tail = 0;
		int n;
		scanf("%d", &n);
		for(int i = 1; i <= n; i++) {
			scanf("%s", keyword);
			insert(keyword, root);
		}
		build_ac_automation(root);
		scanf("%s", str);
		printf("%d\n", query(str, root));
	}
	return 0;
}  

/*
1
5
she
he
say
shr
her
yasherhs
*/