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 <cstdio>
#include <iostream>
#include <stack>
#define MAX_VERTEXES 100
#define ZERO 0
#define NIL -1

using namespace std;

//think easy make easy

int n;//num of vertexes(頂点)
int matrix_graph[MAX_VERTEXES+1+1][MAX_VERTEXES+1+1];//1オリジン

stack<int> stk;
bool discovered[MAX_VERTEXES+1+1];//1オリジン
int discovered_time[MAX_VERTEXES+1+1];
int completed_time[MAX_VERTEXES+1+1];
int current_time = 0;

void DFS(int v){
	int v_tmp;
	for(int i=1;i<=n;i++){
		//if(i == v);
		if(matrix_graph[v][i] == 1 && !discovered[i]){
			current_time++;
			discovered_time[i] = current_time;
			stk.push(v);
			matrix_graph[v][i] == 0;
			discovered[i] = true;
			DFS(i);
		}else if(matrix_graph[v][i] == 1 && discovered[i]){
			matrix_graph[v][i] == 0;
		}

		if(i == n){
			current_time++;
			completed_time[v] = current_time;
			//if(!stk.empty())
			//{
				//cout <<stk.top() <<endl;
				//v_tmp = stk.top();
				//stk.pop();
				//DFS(v_tmp);
			//}
		}
	}
}

int main(){
	scanf("%d",&n);

	int v_num;
	int k;//v_numの出次数

	for(int i=1;i<=n;i++){
		for(int j=1;j<=n;j++){
			matrix_graph[i][j] = ZERO;
		}
	}

	for(int i=0;i<n;i++){
		scanf("%d",&v_num);
		scanf("%d",&k);

		for(int j=0;j<k;j++){
			int v_num2;
			scanf("%d",&v_num2);
			matrix_graph[v_num][v_num2] = 1;
		}
	}

	for(int i=1;i<=n;i++){
		discovered[i] = false;
		discovered_time[i] = NIL;
		completed_time[i] = NIL;
	}

	for(int i=1;i<=n;i++){
		current_time++;
		if(!discovered[i]){
			discovered[i] = true;
			discovered_time[i] = current_time;
			DFS(i);
		}
	}

	for(int i=1;i<=n;i++){
		cout <<i <<" " <<discovered_time[i] <<" " <<completed_time[i] <<endl;
	}

	return 0;
}

C++: #include <iostream>
using namespace std;

int r[101][101];
int d[101], f[101], num, visit[100]={0}, p=0;

void dfs(int n){
    if(visit[n]!=1){
        visit[n] = 1;
        d[n] = ++p;
        for(int i=1; i<num+1; i++)
            if(r[n][i]==1) dfs(i);
        f[n] = ++p;
    }
}

int main(void){
    int u, k, v;
    cin >> num;
    for(int i=0; i<num; i++){
        cin >> u >> k;
        for(int j=0; j<k; j++){
            cin >> v;
            r[u][v]=1;
        }
    }
    for(int i=1; i<num+1; i++){
        if(visit[i]!=1) dfs(i);
    }
    for(int i=1; i<num+1; i++)
        cout << i << " " << d[i] << " " << f[i] << endl;
    return 0;
}

C++: #include<stdio.h>
#define N 100
#define WHITE 0
#define GRAY 1
#define BLACK 2

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

void dfs_visit(int u) {
    int v;
    color[u] = GRAY;
    d[u] = ++tt;
    for ( v = 0; v < n; v++) {
        if (M[u][v] == 0 ) continue;
        if (color[v] == WHITE ) {
            dfs_visit(v);
        }
    }
    color[u] = BLACK;
    f[u] = ++tt;
}

void dfs() {
    int u;
    for ( u = 0; u < n; u++) {
        if ( color[u] == WHITE ) dfs_visit(u);
    }
    for (u = 0; u < n; u++) {
        printf("%d %d %d\n", u + 1, d[u], f[u]);
    }
}

int main() {
    int u, v, k, i, j;
    
    scanf("%d", &n);
    for (i = 0; i < n; i++) {
        for (j = 0; j < n; j++) M[i][j] = 0;
    }
    
    for (i = 0; i < n; i++) {
        scanf("%d %d", &u, &k);
        u--;
        for ( j = 0; j < k; j++) {
            scanf("%d", &v);
            v--;
            M[u][v] = 1;
        }
    }
    
    dfs();
    
    return 0;
}

C++: #include<iostream>
#include<algorithm>
using namespace std;

struct VRTX {
	int dt, ft, v[101];
};

int curtime = 1;
VRTX ver[101];

void depthFirstSearch(int u);

int main() {
	int i, j, n, u, k;

	cin >> n;
	for (i = 0; i < n; i++) {
		cin >> u >> k;
		for (j = 0; j < k; j++) {
			cin >> ver[u].v[j];
		}
	}

	depthFirstSearch(1);

	for (i = 1; i <= n; i++) {
		cout << i << " " << ver[i].dt << " " << ver[i].ft << endl;
	}

	return 0;
}

void depthFirstSearch(int u) {
	int i = 0;

	if (ver[u].dt == 0) {
		ver[u].dt = curtime++;

		while (ver[u].v[i] != 0) {
			depthFirstSearch(ver[u].v[i]);
			i++;
		}

		ver[u].ft = curtime++;
	}
}

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

using namespace std;

int n;
vector<vector<int>> g; 
int time = 0;
vector<int> d, f;
 
void dfs(int node){
    time++;

    if(d[node] == 0){
        d[node] = time;
    }

    for(auto next : g[node]){
        if(d[next] == 0){
            dfs(next);
        }
    }
    
    time++;
    if(f[node] == 0){
        f[node] = time;
    }
}
    
int main(){
    
    cin >> n;

    d.assign(n + 1, 0);
    f.assign(n + 1, 0);

    g.assign(n + 1, vector<int>());

    for(int i = 0; i < n; i++)
    {
        int nod, numOut;
        cin  >> nod >> numOut;
        for(int j = 0; j < numOut; j++)
        {
            int temp;
            cin >> temp;
            g[nod].push_back(temp);
        }
    }
    
    dfs(1);

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

    return 0;
}

C++: #include <iostream>
#include <vector>
#include <stdio.h>

using namespace std;

int n, u, k, v, t;
int adjList[101][101];
int adjNum[101];
bool visited[101];

int d[101], f[101];

void dfs(int u) {
    if (visited[u]) return;
    visited[u] = true;

    d[u] = t;
    t++;

    for (int i = 0; i < adjNum[u]; ++i) {
        dfs(adjList[u][i]);
    }

    f[u] = t;
    t++;

}

int main () {
	scanf("%d", &n);

    for (int i = 0; i < n; ++i) {
        scanf("%d %d", &u, &k);
        adjNum[u-1] = k;
        for (int j = 0; j < k; ++j) {
            scanf("%d", &v);
            adjList[u-1][j] = v-1; // all IDs start from 1
        }
    }

    t = 1;
    for (int u = 0; u < n; ++u) {
        dfs(u);
        cout << u+1 << " " << d[u] << " " << f[u] << "\n";
    }

	return 0;
}