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

func dfs(currentId vertexId, timestamp int, vertices []vertex) int {
	currentVertex := &vertices[currentId-1]
	if currentVertex.isVisited() {
		return timestamp
	}
	timestamp = timestamp + 1
	currentVertex.firstVisitAt = timestamp
	for _, adjId := range currentVertex.adjs {
		timestamp = dfs(adjId, timestamp, vertices)
	}
	timestamp = timestamp + 1
	currentVertex.finishVisitAt = timestamp
	return timestamp
}

func solveDfs(vertices []vertex) {
	timestamp := 0
	for {
		vid := vertexId(-1)
		for i := 0; i < len(vertices); i++ {
			if !vertices[i].isVisited() {
				vid = vertexId(i+1)
				break
			}
		}
		if vid > 0 {
			timestamp = dfs(vid, timestamp, vertices)
		} else {
			break
		}
	}
}

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)
	}

	solveDfs(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 <vector>
#include <stack>

using namespace std;

struct Node {
    int visit = 0;
    vector<int> next;
    int s = 0;
    int start = 0;
    int end = 0;
};

int main() {
    int n, id, k, temp, time = 1;
    Node node[101];
    stack<int> st;

    cin >> n;
    for (int i = 0; i < n; i++) {
        cin >> id >> k;
        for (int j = 0; j < k; j++) {
            cin >> temp;
            node[id].next.push_back(temp);
        }
    }

    while (1) {
        int s = -1;
        for (int i = 1; i <= n; i++) {
            if (node[i].visit == 0) {
                s = i;
                break;
            }
        }
        if (s == -1) {
            break;
        }
        
        node[s].start = time++;
        node[s].visit = 1;
        st.push(s);
        while (!st.empty()) {
            temp = st.top();
            if (node[temp].s < node[temp].next.size()) {
                if (node[node[temp].next[node[temp].s]].visit == 0) {
                    node[node[temp].next[node[temp].s]].start = time++;
                    node[node[temp].next[node[temp].s]].visit = 1;
                    st.push(node[temp].next[node[temp].s++]);
                }
                else {
                    node[temp].s++;
                }
            }
            else {
                node[temp].visit = 2;
                node[temp].end = time++;
                st.pop();
            }
        }
    }

    for (int i = 1; i <= n; i++) {
        cout << i << " " << node[i].start << " " << node[i].end << endl;
    }

    return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
#define int long long
vector<vector<int> > G;
int d[111],f[111],u[111];
void dfs(int v,int& p){
  if(u[v]) return;
  u[v]=1;
  sort(G[v].begin(),G[v].end());
  d[v]=++p;
  for(int u:G[v]) dfs(u,p);
  f[v]=++p;
}
signed main(){
  int n;
  cin>>n;
  G.resize(n,vector<int>());
  for(int i=0;i<n;i++){
    int u,k;
    cin>>u>>k;
    u--;
    for(int j=0;j<k;j++){
      int c;
      cin>>c;
      c--;
      G[u].push_back(c);
    }
  }
  int p=0;
  for(int i=0;i<n;i++)
    if(!u[i]) dfs(i,p);
  for(int i=0;i<n;i++) cout<<i+1<<" "<<d[i]<<" "<<f[i]<<endl;;
  return 0;
}

C++: #include <bits/stdc++.h>
#define ll long long
using namespace std;

struct ver{
    ll d;
    ll f;
};

ll t=0;
vector<vector<ll>> mat;
vector<ver> vers;

void find(ll pos) {
    if(vers[pos].d == 0){
        t++;
        vers[pos].d = t;
    }
    for(ll i:mat[pos]) {
        find(i);
    }
    if(vers[pos].f == 0) {
        t++;
        vers[pos].f = t;
    }
}

int main() {
    ll n;
    cin >> n;
    for(ll i=0;i<n;i++) {
        ll u,k;
        cin>>u>>k;
        vector<ll> aaa;
        for(ll j=0;j<k;j++) {
            ll tmp;
            cin>>tmp;
            aaa.push_back(tmp-1);
        }
        mat.push_back(aaa);
    }
    for(ll i=0;i<n;i++) {
        vers.push_back(ver{0,0});
    }
    find(0);
    for(ll i=0;i<n;i++) {
        cout << i+1<<" "<<vers[i].d<<" "<<vers[i].f<<endl;
    }
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <stack>

using namespace std;

const int max_v = 100;
vector<vector<int>> adj_list;
int d[max_v] = { 0 };
int f[max_v] = { 0 };
int discovered[max_v] = { 0 };
int time = 1;

// Depth-first Search ( Stack implementation)
void DFS(int v)
{
	stack<int> S;
	S.push(v);
	discovered[v] = 1;
	d[v] = time++;
	int i = 0;
	while (!S.empty()) {
		v = S.top();
		if (i < adj_list[v - 1].size()) {
			int u = adj_list[v - 1][i++];
			if (discovered[u] == 0) {
				discovered[u] = 1;
				d[u] = time++;
				S.push(u);
				i = 0;
			}
		}
		else {
			S.pop();
			f[v] = time++;
			i = 0;
		}
	}
}

int main(int argc, char** argv)
{
	// Input
	int n;
	int u, k;
	cin >> n;
	for (int i = 0; i < n; i++) {
		cin >> u >> k;
		int v;
		vector<int> adj;
		for (int j = 0; j < k; j++) {
			cin >> v;
			adj.push_back(v);
		}
		adj_list.push_back(adj);
	}

	// Depth-first Search
	DFS(1);

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

	return 0;
}

C++: #include <iostream>
#include <string>
#include <sstream>
#include <list>
#include <stack>
#include <queue>
#include <algorithm>
#include <utility>
#include <vector>
#include <map>
#include <bitset>
#include <cstring>
#include <cstdio>
#include <cmath>

using namespace std;

struct dd{
    int d,f;
    dd(){
        d=0;
        f=0;
    }
};
bool data[101][101]={};
void f1(dd*,int,int&,int);

int main()
{
    int N,M,num1,num2;
    dd ddata[101]={};
    cin>>N;
    for(int i=0;i<N;i++){
        cin>>num1;
        cin>>M;
        for(int j=0;j<M;j++){
            cin>>num2;
            data[num1][num2]=true;
        }
    }
    int time=1;
    for(int i=1;i<=N;i++){
        if(!ddata[i].d)f1(ddata,i,time,N);
    }
    for(int i=1;i<=N;i++){
        cout<<i<<' '<<ddata[i].d;
        if(ddata[i].d){
            cout<<' '<<ddata[i].f;
        }
        cout<<endl;
    }
}
void f1(dd* ddata,int num,int& time,int N)
{
    if(!ddata[num].d)ddata[num].d=time++;
    data[num][num]=false;
    for(int i=1;i<=N;i++){
        if(data[num][i]){
            data[num][i]=false;
            data[i][num]=false;
            f1(ddata,i,time,N);
        }
    }
    if(!ddata[num].f)ddata[num].f=time++;
}