【洛谷P2444】【POI2000】—病毒（Ac自动机）

传送门

很显然就是从$Ac$自动机根开始走不经过任何一个终点有一个环

记得建$fail$的时候下传终点标记

#include<bits/stdc++.h>
using namespace std;
const int RLEN=1<<20|1;
inline char gc(){
    static char ibuf[RLEN],*ib,*ob;
    (ob==ib)&&(ob=(ib=ibuf)+fread(ibuf,1,RLEN,stdin));
    return (ob==ib)?EOF:*ib++;
}
#define gc getchar
inline int read(){
    char ch=gc();
    int res=0,f=1;
    while(!isdigit(ch))f^=ch=='-',ch=gc();
    while(isdigit(ch))res=(res+(res<<2)<<1)+(ch^48),ch=gc();
    return f?res:-res;
}
#define ll long long
#define re register
#define pii pair<int,int>
#define fi first
#define se second
#define pb push_back
#define cs const
#define bg begin
#define poly vector<int>
#define chemx(a,b) ((a)<(b)?(a)=(b):0)
#define chemn(a,b) ((a)>(b)?(a)=(b):0)
cs int N=30005;
namespace Ac{
	int nxt[N][2],fail[N],vis[N],vt[N],tot,ed[N];
	inline void insert(char *s){
		int p=0;
		for(int i=1,len=strlen(s+1);i<=len;i++){
			int c=s[i]-'0';
			if(!nxt[p][c])nxt[p][c]=++tot;
			p=nxt[p][c];
		}
		ed[p]=1;
	}
	queue<int> q;
	inline void buildfail(){
		for(int i=0;i<=1;i++){
			if(nxt[0][i])q.push(nxt[0][i]);
		}
		while(!q.empty()){
			int p=q.front();q.pop();
			for(int c=0;c<=1;c++){
				int v=nxt[p][c];
				if(v)fail[v]=nxt[fail[p]][c],q.push(v),ed[v]|=ed[fail[v]];
				else nxt[p][c]=nxt[fail[p]][c];
			}
		}
	}
	bool dfs(int u){
		vis[u]=vt[u]=1;
		bool res=0;
		for(int i=0;i<=1;i++){
			int v=nxt[u][i];
			if(ed[v])continue;
			if(vis[v])return true;
			if(vt[v])continue;
			if(dfs(v))return true;
		}
		vis[u]=0;
		return false;
	}
	inline bool findloop(){
		return dfs(0);
	}
}
int n;
char s[2005];
int main(){
	n=read();
	for(int i=1;i<=n;i++){
		scanf("%s",s+1);
		Ac::insert(s);
	}
	Ac::buildfail();
	if(Ac::findloop())cout<<"TAK
";
	else cout<<"NIE
";
}