[BZOJ1823][JSOI2010]满汉全席（2-SAT）

题目描述

题解

代码

#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdio>
#include<cmath>
using namespace std;
#define N 2005

int T,n,m,cnt,dfs_clock,top,scc;
char s1,s2;
int tot,point
,nxt
,v
;
int pt
[2],id
,jd
,x
,y
,dfn
,low
,stack
,belong
;
bool vis
,flag;

void clear()
{
n=m=cnt=dfs_clock=top=scc=0;
tot=0;memset(point,0,sizeof(point));
memset(dfn,0,sizeof(dfn));memset(low,0,sizeof(low));memset(belong,0,sizeof(belong));memset(vis,0,sizeof(vis));
}
void add(int x,int y)
{
++tot; nxt[tot]=point[x]; point[x]=tot; v[tot]=y;
}
void tarjan(int x)
{
dfn[x]=low[x]=++dfs_clock;stack[++top]=x;vis[x]=1;
for (int i=point[x];i;i=nxt[i])
if (!dfn[v[i]])
{
tarjan(v[i]);
low[x]=min(low[x],low[v[i]]);
}
else if (vis[v[i]])
low[x]=min(low[x],dfn[v[i]]);
if (dfn[x]==low[x])
{
int now=0;++scc;
while (now!=x)
{
now=stack[top--];
vis[now]=0;
belong[now]=scc;
}
}
}
int main()
{
scanf("%d",&T);
while (T--)
{
clear();
scanf("%d%d\n",&n,&m);
cnt=0;
for (int i=1;i<=n;++i) pt[i][0]=++cnt,pt[i][1]=++cnt;
for (int i=1;i<=m;++i)
{
scanf("%c%d %c%d\n",&s1,&id[i],&s2,&jd[i]);
if (s1=='m') x[i]=0; else x[i]=1;
if (s2=='m') y[i]=0; else y[i]=1;
add(pt[id[i]][x[i]^1],pt[jd[i]][y[i]]);
add(pt[jd[i]][y[i]^1],pt[id[i]][x[i]]);
}
for (int i=1;i<=n;++i)
if (!dfn[i]) tarjan(i);
flag=1;
for (int i=1;i<=n;++i)
{
if (!belong[pt[i][0]]&&!belong[pt[i][1]]) continue;
if (belong[pt[i][0]]==belong[pt[i][1]]) {flag=0;break;}
}
if (flag) puts("GOOD");
else puts("BAD");
}
}