Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

type vertexId int

type vertex struct {
	id vertexId
	firstVisitAt int
	finishVisitAt int
	adjs []vertexId
}

func createVertex(id int, adjsInt []int) vertex {
	adjs := make([]vertexId, len(adjsInt))
	for i := 0; i < len(adjs); i++ {
		adjs[i] = vertexId(adjsInt[i])
	}
	return vertex{
		id: vertexId(id),
		firstVisitAt: 0,
		finishVisitAt: 0,
		adjs: adjs,
	}
}

func (v *vertex) doesAllAdjsVisited(vertices []vertex) bool {
	for _, vId := range v.adjs {
		adj := vertices[vId-1]
		if !adj.isVisited() {
			return false
		}
	}
	return true
}

func (v *vertex) isFirstVisit() bool {
	return v.firstVisitAt == 0
}

func (v *vertex) isVisited() bool {
	return v.firstVisitAt > 0
}

func (v *vertex) nextVertex(vertices []vertex) (vertexId, error) {
	for _, vId := range v.adjs {
		adj := vertices[vId-1]
		if !adj.isVisited() {
			return vId, nil
		}
	}
	return vertexId(-1), fmt.Errorf("illegal")
}

func dfs(currentId vertexId, timestamp int, vertices []vertex) int {
	timestamp = timestamp + 1
	currentVertex := &vertices[currentId-1]
	if currentVertex.isFirstVisit() {
		currentVertex.firstVisitAt = timestamp
	}
	for !currentVertex.doesAllAdjsVisited(vertices) {
		nextVertexId, _ := currentVertex.nextVertex(vertices)
		timestamp = dfs(nextVertexId, timestamp, vertices)
	}
	timestamp = timestamp + 1
	currentVertex.finishVisitAt = timestamp
	return timestamp
}

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)

	n, err := nextInt(sc)
	if err != nil {
		panic(err)
	}

	vertices := make([]vertex, n)
	for i := 0; i < n; i++ {
		id, err := nextInt(sc)
		if err != nil {
			panic(err)
		}
		adjN, err := nextInt(sc)
		if err != nil {
			panic(err)
		}
		adjs := make([]int, adjN)
		for j := 0; j < adjN; j++ {
			adjId, err := nextInt(sc)
			if err != nil {
				panic(err)
			}
			adjs[j] = adjId
		}
		vertices[i] = createVertex(id, adjs)
	}

	dfs(vertexId(1), 0, vertices)

	for i := 0; i < n; i++ {
		fmt.Printf("%d %d %d\n", vertices[i].id, vertices[i].firstVisitAt, vertices[i].finishVisitAt)
	}
}

func nextText(sc *bufio.Scanner) string {
	sc.Scan()
	return sc.Text()
}

func nextInt(sc *bufio.Scanner) (int, error) {
	return strconv.Atoi(nextText(sc))
}

C++: #include <iostream>
#include <string>
#include <map>
#include <stack>
#include <algorithm>
using namespace std;
#define MAX 100000

static const int N=100;
static const int WHITE=0;
static const int GRAY=1;
static const int BLACK=2;

int n, M[N][N];
int color[N],d[N],f[N],tt;
int nt[N];

int next(int u){
  for(int v=nt[u];v<n;v++){
    nt[u]=v+1;
    if(M[u][v]) return v;
  }
  return -1;
}

void dfs_visit(int r){
  for(int i=0;i<n;i++) nt[i]=0;
  stack<int> S;
  S.push(r);
  color[r]=GRAY;
  d[r]=++tt;
  while(!S.empty()){
    int u=S.top();
    int v=next(u);
    if(v!=-1){
      if(color[v]=WHITE){
        color[v]=GRAY;
        d[v]=++tt;
        S.push(v);
      }
      else{
        S.pop();
        color[u]=BLACK;
        f[u]=++tt;
      }
    }
  }
}

void dfs(){
  for(int i=0;i<n;i++){
    color[i]=WHITE;
    nt[i]=0;
  }
  tt=0;

  for(int u=0;u<n;u++){
    if(color[u]==WHITE) dfs_visit(u);
  }
  for(int i=0;i<n;i++){
    cout << i+1 << " " << d[i] << " " << f[i] << endl;
  }
}

int main(){
  int u,k,v;
  cin >> n;
  
  for(int i=0;i<n;i++){
    for(int j=0;j<n;j++){
      M[i][j]=0;
    }
  }

  for(int i=0;i<n;i++){
    cin >> u >> k;
    u--;
    for(int j=0;j<k;j++){
      cin >> v;
      v--;
      M[u][v]=1;
    }
  }
  dfs();
  return 0;
}

C++: // J4180449 三宅亮輔
// 問題名
// - Depth First Search
// 問題URL
// - https://onlinejudge.u-aizu.ac.jp/#/problems/ALDS1_11_B
// 所要時間
// - 35分
// 学んだこと
//  どこで時間を更新するのかの理解に苦しんだ
//  番号が小さい順に巡ることをソートで実装しようとしたが必要ないと気づいて楽になった
//  再帰関数のスマートさに感動した

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

int n;

vector<int> v[100];
bool visited[100];
int d[100];
int f[100];

int dfs(int i, int now) {
    visited[i] = true;
    now++;
    d[i] = now;
    for(int j = 0; j < v[i].size(); j++) {
        if(!visited[v[i][j]])
            now = dfs(v[i][j], now);
    }
    now++;
    f[i] = now;
    return now;
}

int main() {
    cin >> n;
    for(int i = 0; i < n; i++) {
        int u, k;
        cin >> u >> k;
        u--;
        for(int j = 0; j < k; j++) {
            int x;
            cin >> x;
            x--;
            v[u].push_back(x);
        }
    }
    int now = 0;
    for(int i = 0; i < n; i++) {
        if(!visited[i])
            now = dfs(i, now);
    }

    for(int i = 0; i < n; i++) {
        cout << i + 1 << " " << d[i] << " " << f[i] << endl;
    }
}

C++: #include<iostream>
using namespace std;
int N,t=0;
int d[101][101],Ts[101],Te[101];
bool visit[101];
void graph(){
    int u,k,a;
    for(int i=1;i<=N;++i){
        cin>>u>>k;
        for(int j=0;j<k;++j){
            cin>>a;
            d[u][a]=1;
        }
        visit[i]=true;
    }
}
void dfs(int cur){
    t+=1;
    Ts[cur]=t;
    visit[cur]=false;
    for(int i=1;i<=N;++i){
        if(d[cur][i]==1&&visit[i]){
            visit[i]=false;
            dfs(i);
         }
    }
    t+=1;
    Te[cur]=t;
}
int main(){
    cin>>N;
    graph();
    dfs(1);
    for(int i=1;i<=N;++i){
        cout<<i<<" "<<Ts[i]<<" "<<Te[i]<<endl;
    }
}