csu oj Infected Computer 1427

 #include <iostream>
 #include <algorithm>
 #include <stdio.h>
 #define max 20005
 #define ll long long
 using namespace std;

 struct G{
     int from;
     int to;
     ll time;
 }game[max];

 bool graf[max];

 bool cmp(G a,G b){
     return a.time < b.time;
 }
 int main()
 {
     int n,m;
     while(cin>>n>>m){
         for(int i = ;i < max;i++){
             graf[i]=false;
             game[i].time=game[i].from=game[i].to=;
         }
         graf[]=true;

         for(int i = ;i < m;i++){
             cin>>game[i].time>>game[i].from>>game[i].to;
         }
         sort(game,game+m,cmp);

         bool flag = false;
         for(int i = ;i < m;i++){
             if(game[i].from==){
                 flag = true;
                 //graf[game[i].to] = true;
             }
             if(flag&&graf[game[i].from]){
                 graf[game[i].to] = true;
             }
         }
         ll ans = ;
         for(int i = ;i <= n;i++){
             if(graf[i])ans++;
         }
         cout<<ans<<endl;
     }
     return ;
 }

如果非要给划分，我想应该是属于并查集一类的