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

Posted on 2016-07-05 23:03  yyjxx2010xyu  阅读(133)  评论(0编辑  收藏  举报

一条边<u,v>表示u选那么v一定被选。

 1 #include <iostream>
 2 #include <cstring>
 3 #include <cstdio>
 4 #include <algorithm>
 5 using namespace std;
 6 const int Maxm=21000;
 7 const int Maxn=2010;
 8 struct EDGE{int to,next;}edge[Maxm];
 9 int T,m,Stack[Maxn],head[Maxn],Belong[Maxn],Id[Maxn],Dfn[Maxn],Low[Maxn],h1,h2,h,Stamp,scc,top,cnt;
10 bool vis[Maxn];
11 inline int Min(int x,int y) {return x>y?y:x;}
12 inline void Add(int u,int v){edge[cnt].to=v;edge[cnt].next=head[u];head[u]=cnt++;}
13 inline bool Check()
14 {
15     for (int i=0;i<T;i++) if (Belong[i<<1]==Belong[i<<1|1]) return false;
16     return true;
17 }
18 void Tarjan(int u)
19 {
20     Stack[++top]=u; vis[u]=true;
21     Low[u]=Dfn[u]=++Stamp;
22     for (int i=head[u];i!=-1;i=edge[i].next)
23         if (Dfn[edge[i].to]==-1) Tarjan(edge[i].to),Low[u]=Min(Low[u],Low[edge[i].to]); else 
24         if (vis[edge[i].to]) Low[u]=Min(Low[u],Dfn[edge[i].to]);
25     if (Dfn[u]==Low[u])
26     {
27         while (true)
28         {
29             int v=Stack[top--];
30             Belong[v]=scc;
31             vis[v]=false;
32             if (u==v) break;
33         }
34         scc++;
35     }
36 }
37 
38 int main()
39 {
40     
41     while (scanf("%d%d",&T,&m)!=EOF)
42     {
43         for (int i=0;i<T;i++)
44         {
45             scanf("%d%d%d",&h,&h1,&h2);
46             Id[h]=i<<1;
47             Id[h1]=Id[h2]=i<<1|1;
48         }
49         memset(head,-1,sizeof(head));
50         memset(Dfn,-1,sizeof(Dfn));
51         cnt=Stamp=top=0;
52         for (int i=1;i<=m;i++)
53         {    
54             scanf("%d%d",&h1,&h2);
55             Add(Id[h1],Id[h2]^1),Add(Id[h2],Id[h1]^1);
56         }
57     
58         for (int i=0;i<T*2;i++) if (Dfn[i]==-1) Tarjan(i);
59         puts(Check()?"yes":"no");
60     }
61     return 0;
62 }
HDU 1824

 

 1 #include <iostream>
 2 #include <cstring>
 3 #include <cstdio>
 4 #include <algorithm>
 5 using namespace std;
 6 const int Maxm=1000100;
 7 const int Maxn=2010;
 8 struct EDGE{int to,next;}edge[Maxm];
 9 int head[Maxn],Dfn[Maxn],Low[Maxn],Belong[Maxn],scc,Stk[Maxn],top,cnt,Stamp,n,m;
10 int p1,p2,c1,c2;
11 bool vis[Maxn];
12 inline int Min(int x,int y) {return x>y?y:x;}
13 inline int Id(int num,int pos){return (num<<1)+pos+1;}
14 inline void Add(int u,int v) {edge[cnt].to=v;edge[cnt].next=head[u];head[u]=cnt++;}
15 inline bool Check()
16 {
17     for (int i=0;i<n;i++) if (Belong[Id(i,0)]==Belong[Id(i,1)]) return false; 
18     return true;
19 }
20 void Tarjan(int u)
21 {
22     Stk[++top]=u; vis[u]=true;
23     Dfn[u]=Low[u]=++Stamp;
24     for (int i=head[u];i!=-1;i=edge[i].next)
25         if (Dfn[edge[i].to]==-1) Tarjan(edge[i].to),Low[u]=Min(Low[u],Low[edge[i].to]); else 
26         if (vis[edge[i].to]) Low[u]=Min(Low[u],Dfn[edge[i].to]);
27     if (Low[u]==Dfn[u])
28     {
29         while (true)
30         {
31             int v=Stk[top--];
32             vis[v]=false;
33             Belong[v]=scc;
34             if (v==u) break;
35         }
36         scc++;
37     }
38 }
39 int main()
40 {
41     while (scanf("%d%d",&n,&m)!=EOF)
42     {
43         memset(head,-1,sizeof(head));
44         memset(Dfn,-1,sizeof(Dfn));
45         memset(Belong,0,sizeof(Belong));
46         cnt=top=scc=0;
47         for (int i=1;i<=m;i++)
48         {
49             scanf("%d%d%d%d",&p1,&p2,&c1,&c2);
50             Add(Id(p1,c1),Id(p2,1-c2)),Add(Id(p2,c2),Id(p1,1-c1));
51         }
52         for (int i=1;i<=2*n;i++) if (Dfn[i]==-1) Tarjan(i);
53         puts(Check()?"YES":"NO");
54     }
55     return 0;
56 }
HDU 3062

 

 1 #include <iostream>
 2 #include <cstring>
 3 #include <cstdio>
 4 #include <algorithm>
 5 using namespace std;
 6 const int Maxn=2010;
 7 const int Maxm=4010000;
 8 int One[Maxn],Zero[Maxn],Stack[Maxn],Belong[Maxn],head[Maxn],Low[Maxn],Dfn[Maxn],n,m,u,v,w,cnt,Stamp,scc,top;
 9 bool vis[Maxn];
10 char ch[20];
11 struct EDGE{int to,next;}edge[Maxm];
12 inline int Min(int x,int y){return x>y?y:x;}
13 inline void Add(int u,int v){edge[cnt].to=v;edge[cnt].next=head[u];head[u]=cnt++;}
14 inline bool Check() 
15 {
16     for (int i=0;i<n;i++) if (Belong[One[i]]==Belong[Zero[i]]) return false;
17     return true;
18 }
19 void Tarjan(int u)
20 {
21     Stack[++top]=u; vis[u]=true;
22     Low[u]=Dfn[u]=++Stamp;
23     for (int i=head[u];i!=-1;i=edge[i].next)
24         if (Dfn[edge[i].to]==-1) Tarjan(edge[i].to),Low[u]=Min(Low[u],Low[edge[i].to]); else 
25         if (vis[edge[i].to]) Low[u]=Min(Low[u],Dfn[edge[i].to]);
26     if (Low[u]==Dfn[u])
27     {
28         while (true)
29         {
30             int v=Stack[top--];
31             vis[v]=false;
32             Belong[v]=scc;
33             if (u==v) break;
34         }
35         scc++;
36     }
37 }
38 int main()
39 {
40     scanf("%d%d",&n,&m);
41     for (int i=0;i<n;i++) One[i]=i<<1,Zero[i]=i<<1|1;
42     memset(head,-1,sizeof(head));
43     memset(Dfn,-1,sizeof(Dfn));
44     for (int i=1;i<=m;i++)
45     {
46         scanf("%d%d%d%s",&u,&v,&w,ch);
47         if (ch[0]=='A')
48         {
49             if (w==1) Add(Zero[u],One[u]),Add(Zero[v],One[v]);
50             if (w==0) Add(One[u],Zero[v]),Add(One[v],Zero[u]);
51         }
52         if (ch[0]=='O')
53         {
54             if (w==1) Add(Zero[u],One[v]),Add(Zero[v],One[u]);
55             if (w==0) Add(One[v],Zero[v]),Add(One[u],Zero[u]);
56         }
57         if (ch[0]=='X')
58         {
59             if (w==1) Add(One[u],Zero[v]),Add(Zero[u],One[v]),Add(Zero[v],One[u]),Add(One[v],Zero[u]);
60             if (w==0) Add(One[u],One[v]),Add(One[v],One[u]),Add(Zero[u],Zero[v]),Add(Zero[v],Zero[u]);
61         }
62     }
63     
64     for (int i=0;i<n<<1;i++) if (Dfn[i]==-1) Tarjan(i);
65     puts(Check()?"YES":"NO");
66     return 0;
67 }
POJ 3678

 

 1 #include <cstdio>
 2 #include <iostream>
 3 #include <cstring>
 4 #include <algorithm>
 5 using namespace std;
 6 const int Maxm=80100;
 7 int Stk[Maxm],Low[Maxm],Dfn[Maxm],head[Maxm],Belong[Maxm],In[Maxm],Out[Maxm],Pos[Maxm];
 8 int cnt,top,Stamp,KASE,scc,n,m,x,u[Maxm],v[Maxm],tot;
 9 bool vis[Maxm];
10 struct EDGE{int to,next;}edge[Maxm<<4];
11 inline int Min(int x,int y) {return x>y?y:x;}
12 inline void Swap(int &x,int &y) {int t=x;x=y;y=t;}
13 inline void Add(int u,int v) {edge[cnt].to=v;edge[cnt].next=head[u];head[u]=cnt++;}
14 inline bool Check()
15 {
16     for (int i=1;i<=m;i++) if (Belong[In[i]]==Belong[Out[i]]) return false;
17     return true;
18 }
19 void Tarjan(int u)
20 {
21     Stk[++top]=u; vis[u]=true;
22     Low[u]=Dfn[u]=++Stamp;
23     for (int i=head[u];i!=-1;i=edge[i].next)
24         if (Dfn[edge[i].to]==-1) Tarjan(edge[i].to),Low[u]=Min(Low[u],Low[edge[i].to]); else
25         if (vis[edge[i].to]) Low[u]=Min(Low[u],Dfn[edge[i].to]);
26     if (Low[u]==Dfn[u])
27     {
28         while (true)
29         {
30             int v=Stk[top--];
31             vis[v]=false;
32             Belong[v]=scc;
33             if (u==v) break;
34         }
35         scc++;
36     }
37 }
38 int main()
39 {
40     scanf("%d",&KASE);
41     for (int Kase=1;Kase<=KASE;Kase++)
42     {
43         scanf("%d%d",&n,&m);
44         for (int i=1;i<=m;i++) scanf("%d%d",&u[i],&v[i]);
45         for (int i=1;i<=n;i++) scanf("%d",&x),Pos[x]=i;
46         if(m>3*n-6){puts("NO");continue;}
47         for (int i=0;i<m;i++) In[i+1]=i<<1,Out[i+1]=i<<1|1;
48         tot=0;
49         for (int i=1;i<=m;i++) 
50         {
51             u[i]=Pos[u[i]],v[i]=Pos[v[i]];
52             if (v[i]<u[i]) Swap(u[i],v[i]);
53             if ((v[i]-u[i]==1) || (v[i]==n && u[i]==1)) continue;
54             u[++tot]=u[i],v[tot]=v[i];
55         }
56         m=tot;
57         memset(Dfn,-1,sizeof(Dfn));
58         memset(head,-1,sizeof(head));
59         memset(vis,false,sizeof(vis));
60         Stamp=cnt=top=scc=0;
61           
62         for (int i=1;i<=m;i++)
63             for (int j=i+1;j<=m;j++)
64                 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])))
65                     Add(In[i],Out[j]),Add(In[j],Out[i]),Add(Out[i],In[j]),Add(Out[j],In[i]);
66                   
67         for (int i=0;i<m<<1;i++) if (Dfn[i]==-1) Tarjan(i);
68         puts(Check()?"YES":"NO");
69     }
70     return 0;
71 }
72 
BZOJ 1997