POJ 1236 Network of Schools

  1 #include <cstdio>
  2 #include <algorithm>
  3 #include <cstring>
  4 #include <map>
  5 using namespace std;
  6 
  7 const int MAXN=10010;
  8 const int MAXM=50010;
  9 
 10 struct Edge{
 11     int to;
 12     int next;
 13 }edge[MAXM];
 14 
 15 int head[MAXN];
 16 int tot;
 17 
 18 void addEdge(int u,int v){
 19     edge[tot].to=v;
 20     edge[tot].next=head[u];
 21     head[u]=tot++;
 22 }
 23 
 24 void init(){
 25     memset(head,-1,sizeof(head));
 26     tot=0;
 27 }
 28 
 29 int LOW[MAXN],DFS[MAXN],Stack[MAXN],Num[MAXN],Belong[MAXN];
 30 bool Instack[MAXN];
 31 int Index;
 32 int scc;
 33 int top;
 34 
 35 void Targan(int u){
 36     LOW[u]=DFS[u]=++Index;
 37     Stack[top++]=u;
 38     Instack[u]=true;
 39 
 40     int v;
 41     for(int i=head[u];i!=-1;i=edge[i].next){
 42         v=edge[i].to;
 43         if(!DFS[v]){
 44             Targan(v);
 45             if(LOW[u]>LOW[v])
 46                 LOW[u]=LOW[v];
 47         }else if(Instack[v]&&LOW[u]>DFS[v]){
 48                 LOW[u]=DFS[v];
 49         }
 50     }
 51 
 52     if(LOW[u]==DFS[u]){
 53         scc++;
 54 
 55         do{
 56             v=Stack[--top];
 57             Instack[v]=false;
 58             Belong[v]=scc;
 59             Num[scc]++;
 60         }while(v!=u);
 61     }
 62 }
 63 
 64 void Solve(int n){
 65     memset(Instack,false,sizeof(Instack));
 66     memset(DFS,0,sizeof(DFS));
 67     memset(Num,0,sizeof(Num));
 68 
 69     Index=scc=top=0;
 70     for(int i=1;i<=n;i++)
 71         if(!DFS[i])
 72         Targan(i);
 73 }
 74 
 75 map<int,int>mp[MAXN];
 76 int out[MAXN],in[MAXN];
 77 int main(){
 78     int n;
 79     while(scanf("%d",&n)!=EOF){
 80         init();
 81 
 82         for(int i=1;i<=n;i++){
 83             int v;
 84             while(scanf("%d",&v)&&v){
 85                 addEdge(i,v);
 86                 mp[i][v]=1;
 87             }
 88         }
 89         Solve(n);
 90          if(scc==1){
 91             printf("1\n0\n");
 92             continue;
 93         }
 94 
 95         for(int i=1;i<=n;i++)
 96         for(int j=1;j<=n;j++){
 97             if(mp[i][j]&&Belong[i]!=Belong[j]){
 98                 out[Belong[i]]++;
 99                 in[Belong[j]]++;
100             }
101         }
102 
103         int ans1=0,ans2=0;
104         for(int i=1;i<=scc;i++){
105             if(in[i]==0) ans1++;
106             if(out[i]==0) ans2++;
107         }
108 
109         printf("%d\n%d\n",ans1,max(ans1,ans2));
110 
111 
112     }
113 }