HDU 3062 && HDU 1824 && POJ 3678 && BZOJ 1997 2-SAT

一条边<u,v>表示u选那么v一定被选。

 #include <iostream>
 #include <cstring>
 #include <cstdio>
 #include <algorithm>
 using namespace std;
 const int Maxm=;
 const int Maxn=;
 struct EDGE{int to,next;}edge[Maxm];
 int T,m,Stack[Maxn],head[Maxn],Belong[Maxn],Id[Maxn],Dfn[Maxn],Low[Maxn],h1,h2,h,Stamp,scc,top,cnt;
 bool vis[Maxn];
 inline int Min(int x,int y) {return x>y?y:x;}
 inline void Add(int u,int v){edge[cnt].to=v;edge[cnt].next=head[u];head[u]=cnt++;}
 inline bool Check()
 {
     for (int i=;i<T;i++) if (Belong[i<<]==Belong[i<<|]) return false;
     return true;
 }
 void Tarjan(int u)
 {
     Stack[++top]=u; vis[u]=true;
     Low[u]=Dfn[u]=++Stamp;
     for (int i=head[u];i!=-;i=edge[i].next)
         if (Dfn[edge[i].to]==-) Tarjan(edge[i].to),Low[u]=Min(Low[u],Low[edge[i].to]); else
         if (vis[edge[i].to]) Low[u]=Min(Low[u],Dfn[edge[i].to]);
     if (Dfn[u]==Low[u])
     {
         while (true)
         {
             int v=Stack[top--];
             Belong[v]=scc;
             vis[v]=false;
             if (u==v) break;
         }
         scc++;
     }
 }

 int main()
 {

     while (scanf("%d%d",&T,&m)!=EOF)
     {
         for (int i=;i<T;i++)
         {
             scanf("%d%d%d",&h,&h1,&h2);
             Id[h]=i<<;
             Id[h1]=Id[h2]=i<<|;
         }
         memset(head,-,sizeof(head));
         memset(Dfn,-,sizeof(Dfn));
         cnt=Stamp=top=;
         for (int i=;i<=m;i++)
         {
             scanf("%d%d",&h1,&h2);
             Add(Id[h1],Id[h2]^),Add(Id[h2],Id[h1]^);
         }

         for (int i=;i<T*;i++) if (Dfn[i]==-) Tarjan(i);
         puts(Check()?"yes":"no");
     }
     return ;
 }

HDU 1824

 #include <iostream>
 #include <cstring>
 #include <cstdio>
 #include <algorithm>
 using namespace std;
 const int Maxm=;
 const int Maxn=;
 struct EDGE{int to,next;}edge[Maxm];
 int head[Maxn],Dfn[Maxn],Low[Maxn],Belong[Maxn],scc,Stk[Maxn],top,cnt,Stamp,n,m;
 int p1,p2,c1,c2;
 bool vis[Maxn];
 inline int Min(int x,int y) {return x>y?y:x;}
 inline int Id(int num,int pos){return (num<<)+pos+;}
 inline void Add(int u,int v) {edge[cnt].to=v;edge[cnt].next=head[u];head[u]=cnt++;}
 inline bool Check()
 {
     for (int i=;i<n;i++) if (Belong[Id(i,)]==Belong[Id(i,)]) return false;
     return true;
 }
 void Tarjan(int u)
 {
     Stk[++top]=u; vis[u]=true;
     Dfn[u]=Low[u]=++Stamp;
     for (int i=head[u];i!=-;i=edge[i].next)
         if (Dfn[edge[i].to]==-) Tarjan(edge[i].to),Low[u]=Min(Low[u],Low[edge[i].to]); else
         if (vis[edge[i].to]) Low[u]=Min(Low[u],Dfn[edge[i].to]);
     if (Low[u]==Dfn[u])
     {
         while (true)
         {
             int v=Stk[top--];
             vis[v]=false;
             Belong[v]=scc;
             if (v==u) break;
         }
         scc++;
     }
 }
 int main()
 {
     while (scanf("%d%d",&n,&m)!=EOF)
     {
         memset(head,-,sizeof(head));
         memset(Dfn,-,sizeof(Dfn));
         memset(Belong,,sizeof(Belong));
         cnt=top=scc=;
         for (int i=;i<=m;i++)
         {
             scanf("%d%d%d%d",&p1,&p2,&c1,&c2);
             Add(Id(p1,c1),Id(p2,-c2)),Add(Id(p2,c2),Id(p1,-c1));
         }
         for (int i=;i<=*n;i++) if (Dfn[i]==-) Tarjan(i);
         puts(Check()?"YES":"NO");
     }
     return ;
 }

HDU 3062

 #include <iostream>
 #include <cstring>
 #include <cstdio>
 #include <algorithm>
 using namespace std;
 const int Maxn=;
 const int Maxm=;
 int One[Maxn],Zero[Maxn],Stack[Maxn],Belong[Maxn],head[Maxn],Low[Maxn],Dfn[Maxn],n,m,u,v,w,cnt,Stamp,scc,top;
 bool vis[Maxn];
 char ch[];
 struct EDGE{int to,next;}edge[Maxm];
 inline int Min(int x,int y){return x>y?y:x;}
 inline void Add(int u,int v){edge[cnt].to=v;edge[cnt].next=head[u];head[u]=cnt++;}
 inline bool Check()
 {
     for (int i=;i<n;i++) if (Belong[One[i]]==Belong[Zero[i]]) return false;
     return true;
 }
 void Tarjan(int u)
 {
     Stack[++top]=u; vis[u]=true;
     Low[u]=Dfn[u]=++Stamp;
     for (int i=head[u];i!=-;i=edge[i].next)
         if (Dfn[edge[i].to]==-) Tarjan(edge[i].to),Low[u]=Min(Low[u],Low[edge[i].to]); else
         if (vis[edge[i].to]) Low[u]=Min(Low[u],Dfn[edge[i].to]);
     if (Low[u]==Dfn[u])
     {
         while (true)
         {
             int v=Stack[top--];
             vis[v]=false;
             Belong[v]=scc;
             if (u==v) break;
         }
         scc++;
     }
 }
 int main()
 {
     scanf("%d%d",&n,&m);
     for (int i=;i<n;i++) One[i]=i<<,Zero[i]=i<<|;
     memset(head,-,sizeof(head));
     memset(Dfn,-,sizeof(Dfn));
     for (int i=;i<=m;i++)
     {
         scanf("%d%d%d%s",&u,&v,&w,ch);
         if (ch[]=='A')
         {
             if (w==) Add(Zero[u],One[u]),Add(Zero[v],One[v]);
             if (w==) Add(One[u],Zero[v]),Add(One[v],Zero[u]);
         }
         if (ch[]=='O')
         {
             if (w==) Add(Zero[u],One[v]),Add(Zero[v],One[u]);
             if (w==) Add(One[v],Zero[v]),Add(One[u],Zero[u]);
         }
         if (ch[]=='X')
         {
             if (w==) Add(One[u],Zero[v]),Add(Zero[u],One[v]),Add(Zero[v],One[u]),Add(One[v],Zero[u]);
             if (w==) Add(One[u],One[v]),Add(One[v],One[u]),Add(Zero[u],Zero[v]),Add(Zero[v],Zero[u]);
         }
     }

     for (int i=;i<n<<;i++) if (Dfn[i]==-) Tarjan(i);
     puts(Check()?"YES":"NO");
     return ;
 }

POJ 3678

 #include <cstdio>
 #include <iostream>
 #include <cstring>
 #include <algorithm>
 using namespace std;
 const int Maxm=;
 int Stk[Maxm],Low[Maxm],Dfn[Maxm],head[Maxm],Belong[Maxm],In[Maxm],Out[Maxm],Pos[Maxm];
 int cnt,top,Stamp,KASE,scc,n,m,x,u[Maxm],v[Maxm],tot;
 bool vis[Maxm];
 struct EDGE{int to,next;}edge[Maxm<<];
 inline int Min(int x,int y) {return x>y?y:x;}
 inline void Swap(int &x,int &y) {int t=x;x=y;y=t;}
 inline void Add(int u,int v) {edge[cnt].to=v;edge[cnt].next=head[u];head[u]=cnt++;}
 inline bool Check()
 {
     for (int i=;i<=m;i++) if (Belong[In[i]]==Belong[Out[i]]) return false;
     return true;
 }
 void Tarjan(int u)
 {
     Stk[++top]=u; vis[u]=true;
     Low[u]=Dfn[u]=++Stamp;
     for (int i=head[u];i!=-;i=edge[i].next)
         if (Dfn[edge[i].to]==-) Tarjan(edge[i].to),Low[u]=Min(Low[u],Low[edge[i].to]); else
         if (vis[edge[i].to]) Low[u]=Min(Low[u],Dfn[edge[i].to]);
     if (Low[u]==Dfn[u])
     {
         while (true)
         {
             int v=Stk[top--];
             vis[v]=false;
             Belong[v]=scc;
             if (u==v) break;
         }
         scc++;
     }
 }
 int main()
 {
     scanf("%d",&KASE);
     for (int Kase=;Kase<=KASE;Kase++)
     {
         scanf("%d%d",&n,&m);
         for (int i=;i<=m;i++) scanf("%d%d",&u[i],&v[i]);
         for (int i=;i<=n;i++) scanf("%d",&x),Pos[x]=i;
         if(m>*n-){puts("NO");continue;}
         for (int i=;i<m;i++) In[i+]=i<<,Out[i+]=i<<|;
         tot=;
         for (int i=;i<=m;i++)
         {
             u[i]=Pos[u[i]],v[i]=Pos[v[i]];
             if (v[i]<u[i]) Swap(u[i],v[i]);
             if ((v[i]-u[i]==) || (v[i]==n && u[i]==)) continue;
             u[++tot]=u[i],v[tot]=v[i];
         }
         m=tot;
         memset(Dfn,-,sizeof(Dfn));
         memset(head,-,sizeof(head));
         memset(vis,false,sizeof(vis));
         Stamp=cnt=top=scc=;

         for (int i=;i<=m;i++)
             for (int j=i+;j<=m;j++)
                 if (((u[i]<u[j] && u[j]<v[i] && v[i]<v[j]) || (u[j]<u[i] && u[i]<v[j] && v[j]<v[i])))
                     Add(In[i],Out[j]),Add(In[j],Out[i]),Add(Out[i],In[j]),Add(Out[j],In[i]);

         for (int i=;i<m<<;i++) if (Dfn[i]==-) Tarjan(i);
         puts(Check()?"YES":"NO");
     }
     return ;
 }
 

BZOJ 1997