[BZOJ1823][JSOI2010]满汉全席（2-SAT）

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题解

代码

#include<cstdio>
#include<cstring>
#include<algorithm>
#define clear(x)(memset(x,0,sizeof(x)))
using namespace std;
int T,n,m,p[210],a[2010],nxt[2010],low[210],w[210],st[210],top,pos[210],tot,cnt;
bool ext[210],flag;
int rev(int x){return (x<=n)?x+n:x-n;}
int get(){
char c=getchar();
int x=0,dlt;
while (c!='m'&&c!='h') c=getchar();
dlt=(c=='m')?0:n;
c=getchar();
while (c<'0'||c>'9') c=getchar();
while (c>='0'&&c<='9'){
x=x*10+c-'0';c=getchar();
}
return x+dlt;
}
void add(int x,int y){
tot++;a[tot]=y;nxt[tot]=p[x];p[x]=tot;
}
void Tarjan(int u){
low[u]=w[u]=++tot;
st[++top]=u;ext[u]=true;
for (int i=p[u];i!=0;i=nxt[i])
if (w[a[i]]==0){
Tarjan(a[i]);
low[u]=min(low[u],low[a[i]]);
}else if (ext[a[i]]==true) low[u]=min(low[u],w[a[i]]);
if (low[u]==w[u]){
int v;++cnt;
do{
v=st[top--];pos[v]=cnt;ext[v]=false;
}while (v!=u);
}
}
int main()
{
scanf("%d",&T);
for (int wer=1;wer<=T;wer++){
clear(p);clear(w);clear(low);
clear(ext);tot=cnt=top=flag=0;
scanf("%d%d",&n,&m);
for (int i=1;i<=m;i++){
int v1=get(),v2=get();
add(rev(v1),v2);
add(rev(v2),v1);
}
for (int i=1;i<=2*n;i++)
if (w[i]==0) Tarjan(i);
for (int i=1;i<=n;i++)
if (pos[i]==pos[rev(i)]){
flag=true;break;
}
if (flag==true) printf("BAD\n");
else printf("GOOD\n");
}
return 0;
}