BZOJ1823：[JSOI2010]满汉全席—

BZOJ1823：[JSOI2010]满汉全席——题解

https://www.lydsy.com/JudgeOnline/problem.php?id=1823

https://www.luogu.org/problemnew/show/P4171

题面太长啦就不粘过来啦！

裸的2-SAT用来练板子的。

显然属于“a和b之间必须选一种”模型，只要a'向b连边，b'向a连边即可。

（被这题读入坑了orz）

#include<cstdio>
#include<queue>
#include<cctype>
#include<cstring>
#include<cmath>
#include<stack>
#include<iostream>
#include<algorithm>
using namespace std;
typedef long long ll;
const int N=1005;
const int M=20005;
struct node{int to,nxt;
}e[M];
int T,n,m,head[N],cnt;
int dfn[N],low[N],t,l;
int to[N];
bool inq[N];
stack<int>q;
inline int neg(int x){if(x>n)return x-n;return x+n;
}
inline void add(int u,int v){e[++cnt].to=v;e[cnt].nxt=head[u];head[u]=cnt;
}
void tarjan(int u){dfn[u]=low[u]=++t;q.push(u);inq[u]=1;for(int i=head[u];i;i=e[i].nxt){int v=e[i].to;if(!dfn[v]){tarjan(v);low[u]=min(low[u],low[v]);}else if(inq[v]){low[u]=min(low[u],dfn[v]);}}if(dfn[u]==low[u]){int v;l++;do{v=q.top();q.pop();inq[v]=0;to[v]=l;}while(u!=v);}
}
inline void init(){cnt=t=l=0;memset(head,0,sizeof(head));memset(dfn,0,sizeof(dfn));
}
inline int get(){int k;char ch=0;while(ch!='m'&&ch!='h')ch=getchar();scanf("%d",&k);if(ch=='h')k+=n;return k;
}
int main(){scanf("%d",&T);while(T--){init();scanf("%d%d",&n,&m);for(int i=1;i<=m;i++){int a=get(),b=get();add(neg(a),b);add(neg(b),a);}for(int i=1;i<=2*n;i++)if(!dfn[i])tarjan(i);bool flag=1;for(int i=1;i<=n&&flag;i++){if(to[i]==to[i+n])flag=0;}if(flag)puts("GOOD");else puts("BAD");}
}