P3808 【模板】AC 自动机（简单版）

题目链接

代码

#include <iostream>
#include <cstdio>
using namespace std;
const int N = 1000010;
int n;
char str[N];
int tr[N][26],cnt[N],idx;
int fail[N],q[N];
void insert (char s[N]) {
	int p = 0;
	for (int i = 0;s[i];i++) {
		int t = s[i] - 'a';
		if (!tr[p][t]) tr[p][t] = ++idx;
		p = tr[p][t];
	}
	cnt[p]++;
}
void get_fail () {
	int hh = 0,tt = -1;
	for (int i = 0;i < 26;i++) {
		if (tr[0][i]) q[++tt] = tr[0][i];
	}
	while (hh <= tt) {
		int t = q[hh++];
		for (int i = 0;i < 26;i++) {
			int p = tr[t][i];
			if (!p) tr[t][i] = tr[fail[t]][i];
			else {
				fail[p] = tr[fail[t]][i];
				q[++tt] = p;
			}
		}
	}
}
int main () {
	scanf ("%d",&n);
	for (int i = 1;i <= n;i++) {
		char x[N];
		scanf ("%s",x);
		insert (x);
	}
	get_fail ();
	scanf ("%s",str);
	int ans = 0;
	for (int i = 0,j = 0;str[i];i++) {
		int t = str[i] - 'a';
		int p = j = tr[j][t];
		while (p && cnt[p]) {  //这里如果某一个点不是单词节点，就可以直接退掉
			ans += cnt[p];
			cnt[p] = 0;
			p = fail[p];
		}
	}
	printf ("%d\n",ans);
    return 0;
}