POJ 3207

  1 #include <iostream>
  2 #include <cstring>
  3 #include <cstdio>
  4 using namespace std;
  5 
  6 const int MAXN=1050;
  7 const int MAXM=1000000;
  8 int n,m;
  9 struct d{
 10     int u,v;
 11 }sv[505];
 12 int dfn[MAXN],low[MAXN],st[MAXN],tot,stop,pat,indx,belong[MAXN];
 13 bool stack[MAXN];
 14 struct e{
 15     int u,v;
 16     int next;
 17 }edge[MAXM];
 18 int head[MAXN];
 19 
 20 void addedge(int u,int v){
 21     edge[tot].u=u;
 22     edge[tot].v=v;
 23     edge[tot].next=head[u];
 24     head[u]=tot++;
 25 }
 26 
 27 void exch(int &x,int &y){
 28     if(x>y){
 29         int tmp=y;
 30         y=x;
 31         x=tmp;
 32     }
 33 }
 34 
 35 bool sure(int i,int k){
 36     int u=sv[k].u;
 37     int v=sv[k].v;
 38     int p=sv[i].u;
 39     int q=sv[i].v;
 40     if(p>=u&&p<=v&&q>=u&&q<=v)
 41     return false;
 42     if(p>=v) return false;
 43     if(q<=u) return false;
 44     if(p<=u&&q>=v) return false;
 45     return true;
 46 }
 47 
 48 void tarjan(int u){
 49     dfn[u]=low[u]=++indx;
 50     stack[u]=true;
 51     st[stop++]=u;
 52     int v;
 53     for(int e=head[u];e!=-1;e=edge[e].next){
 54         v=edge[e].v;
 55         if(dfn[v]==0){
 56             tarjan(v);
 57             low[u]=min(low[u],low[v]);
 58         }
 59         else if(stack[v]){
 60             low[u]=min(low[u],dfn[v]);
 61         }
 62     }
 63     if(dfn[u]==low[u]){
 64         pat++;
 65         do{
 66             v=st[--stop];
 67             belong[v]=pat;
 68             stack[v]=false;
 69         }while(u!=v);
 70     }
 71 }
 72 
 73 int main(){
 74     int u,v;
 75     while(scanf("%d%d",&n,&m)!=EOF){
 76         tot=indx=pat=stop=0;
 77         for(int i=0;i<m*2;i++){
 78             dfn[i]=low[i]=belong[i]=0;
 79             stack[i]=false; head[i]=-1;
 80         }
 81         
 82         for(int i=0;i<m;i++){
 83             scanf("%d%d",&sv[i].u,&sv[i].v);
 84             exch(sv[i].u,sv[i].v);
 85             if(i>0){
 86                 for(int k=0;k<i;k++){
 87                     if(sure(i,k)){
 88                         addedge(2*i,2*k+1);
 89                         addedge(2*k,2*i+1);
 90                         addedge(2*i+1,2*k);
 91                         addedge(2*k+1,2*i);
 92                     }
 93                 }
 94             }
 95         }
 96         
 97         for(int i=0;i<2*m;i++)
 98         if(dfn[i]==0)
 99         tarjan(i);
100         
101         bool flag=true;
102         for(int i=0;i<m;i++){
103             if(belong[i*2]==belong[2*i+1]){
104                 flag=false;
105                 printf("the evil panda is lying again\n");
106                 break;
107             }
108         }
109         if(flag)
110         printf("panda is telling the truth...\n");
111     }
112     return 0;
113 }