Codeforces Round #656 (Div. 3) E. Directing Edges 拓扑排序

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
vector<int >g[200005];
int du[200005];
int td[200005];
pair<int ,int >a[200005];
void solve(){
    int n,m;
    cin>>n>>m;
    for(int i=1;i<=n;i++){
        g[i].clear();
        du[i]=0;
        td[i]=0;
    }
    for(int i=1;i<=m;i++){
        int q,x,y;
        cin>>q>>x>>y;
        a[i]=make_pair(x,y);
        if(q){
            g[x].push_back(y);
            du[y]++;
        }
    }
    queue<int >q;
    ll tot=0;
    for(int i=1;i<=n;i++){
        if(!du[i]){
            q.push(i);
        }
    }
    while(!q.empty()){
        int temp=q.front();
        q.pop();
        td[temp]=++tot;
        for(auto i:g[temp]){
            du[i]--;
            if(!du[i]){
                q.push(i);
            }
        }
    }
    if(tot<n){
        cout<<"NO"<<endl;
    }
    else{
        cout<<"YES"<<endl;
        for(int i=1;i<=m;i++){
            int u=a[i].first;
            int v=a[i].second;
            if(td[u]<td[v])cout<<u<<" "<<v<<endl;
            else{
                cout<<v<<" "<<u<<endl;
            } 
        }
    }
}
int main(){
    int t;
    cin>>t;
    while(t--){
        solve();
    }
}

https://codeforces.ml/contest/1385/standings/friends/true