Go: package main

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

type TimeRecord struct {
	discoverTime int
	finishTime   int
}

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

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

	timeRecordMap := make([]TimeRecord, n)
	childrenMap := make([][]int, n)
	for i := 1; i <= n; i++ {
		node, err := nextInt(sc)
		if err != nil {
			panic(err)
		}
		timeRecordMap[node-1] = TimeRecord{-1, -1}

		childNum, err := nextInt(sc)
		if err != nil {
			panic(err)
		}
		childrenMap[node-1] = make([]int, childNum)
		for j := 0; j < childNum; j++ {
			child, err := nextInt(sc)
			if err != nil {
				panic(err)
			}
			childrenMap[node-1][j] = child
		}
	}

	timer := 1
	for {
		startNode := findStartNode(childrenMap, timeRecordMap)
		if startNode > 0 {
			visit(startNode, &timer, childrenMap, timeRecordMap)
		} else {
			break
		}
	}
	for k, v := range timeRecordMap {
		fmt.Printf("%d %d %d\n", k+1, v.discoverTime, v.finishTime)
	}
}

func findStartNode(childrenMap [][]int, timeRecordMap []TimeRecord) int {
	x := -1
	for node, timeRecord := range timeRecordMap {
		if timeRecord.discoverTime < 0 {
			x = node + 1
			break
		}
	}
	if x < 0 {
		return -1
	}

	found := false
	i := 0
	for i < len(childrenMap) {
		children := childrenMap[i]
		for j := 0; j < len(children); j++ {
			if children[j] == x {
				x = j + 1
				found = true
				break
			}
		}
		if found {
			i = 0
		} else {
			i++
		}
	}
	return x
}

func visit(currentNode int, timer *int, childrenMap [][]int, timeRecordMap []TimeRecord) {
	if timeRecordMap[currentNode-1].discoverTime > 0 {
		return
	}
	children := childrenMap[currentNode-1]
	timeRecordMap[currentNode-1] = TimeRecord{*timer, timeRecordMap[currentNode-1].finishTime}
	(*timer)++
	for i := 0; i < len(children); i++ {
		visit(children[i], timer, childrenMap, timeRecordMap)
	}
	timeRecordMap[currentNode-1] = TimeRecord{timeRecordMap[currentNode-1].discoverTime, *timer}
	(*timer)++
}

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

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

using Graph = std::vector<std::vector<int>>;

void dfs(std::vector<bool> &seen, Graph &g, int v, int &time, std::vector<int> &preOrder, std::vector<int> &postOrder){
    preOrder.at(v) = time;
    ++time;

    seen.at(v) = true;
    for(auto nextV : g.at(v)){
        if(seen.at(nextV)){
            continue;
        }
        dfs(seen, g, nextV, time, preOrder, postOrder);
    }

    postOrder.at(v) = time;
    ++time;
}

int main(){
    int n;
    std::cin >> n;

    Graph g(n);
    std::vector<int> preOrder(n), postOrder(n);
    for(int i = 0; i < n; ++i){
        int m, l;
        std::cin >> m >> l;
        for(int j = 0; j < l; ++j){
            int k;
            std::cin >> k;

            g.at(i).push_back(k - 1); 
//            g.at(k - 1).push_back(i); // for undirected graphs
        }
    }

    std::vector<bool> seen(n, false);
    int time = 1;
    for(int i = 0; i < n; ++i){
        if(seen.at(i)){
            continue;
        }

        dfs(seen, g, i, time, preOrder, postOrder);
    }

    for(int i= 0; i < n; ++i){
        std::cout << i + 1 << " " << preOrder.at(i) << " " << postOrder.at(i) << std::endl;
    }

    return 0;
}

C++: #include <algorithm>
#include <iostream>
#include <map>
#include <sstream>
#include <vector>

using namespace std;

map<int, vector<int>> V;
map<int, int> pre;
map<int, int> post;
int t = 1;

int _DFS(int v, vector<bool> &visited) {
  pre[v] = t;
  ++t;
  for (int out_nbr_id : V[v]) {
    if (!visited[out_nbr_id]) {
      visited[out_nbr_id] = true;
      _DFS(out_nbr_id, visited);
    }
  }
  post[v] = t;
  ++t;
}

int main() {
  int n;
  cin >> n;

  vector<bool> visited(n, false);

  cin.ignore();

  for (string line; getline(cin, line);) {
    istringstream is{line};
    int id, n_nbrs, nbr;
    is >> id >> n_nbrs;
    vector<int> out_nbrs;
    while (is >> nbr)
      out_nbrs.push_back(nbr);
    V[id] = out_nbrs;
  }

  for (auto vadj : V) {
    if (!visited[vadj.first]) {
      visited[vadj.first] = true;
      _DFS(vadj.first, visited);
    }
  }

  for (auto vadj : V) {
    int id = vadj.first;
    cout << id << " " << pre[id] << " " << post[id] << endl;
  }
}

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

using namespace std;

const int WHITE = 0, GREY = 1, BLACK = 2;

struct DFS {
    int n;
    vector<vector<int>> g;
    vector<int> color;
    vector<int> dt;
    vector<int> ft;
    int ct = 1;
 
    DFS(int n) : n(n) {
        g.assign(n, vector<int>());
        color.assign(n, WHITE);
        dt.assign(n, -1);
        ft.assign(n, -1);
    }
    
    void solve() {
        for (int i = 0; i < n; i++) {
            if (color[i] == WHITE) {
                dfs(i);
            }
        }
    }
    
    void dfs(int u) {
        //cout << "visit " << u << endl;
        color[u] = GREY;
        dt[u] = ct++; 
        for (int v : g[u]) {
            if (color[v] == WHITE) {
                dfs(v);
            }
        }
        ft[u] = ct++;
        color[u] = BLACK;
    }
    
    void addEdge(int u, int v) {
        g[u].push_back(v);
    }
    
    void printGraph() {
        for (int i = 0; i < n; i++) {
            cout << i << ": ";
            for (int v : g[i]) {
                cout << v << " ";
            }
            cout << endl;
        }
    }
        
};


int main() {   
    int n;
    cin >> n;
    DFS dfs(n);
   
    for (int i = 0; i < n; i++) {
        int u, k;
        cin >> u >> k;
        u--;
        for (int j = 0; j < k; j++) {
            int v;
            cin >> v;
            v--;
            dfs.addEdge(u, v);
        }  
    }
    
    //dfs.printGraph();
    
    dfs.solve();
    
    for (int i = 0; i < n; i++) {
        cout << (i + 1) << " " << dfs.dt[i] << " " << dfs.ft[i] << endl;
    }
    
    return 0;
}

C++: #include <iostream>
#include <vector>
#include <cstring>
#define N 101

using namespace std;

int visited[N], discovery[N], finish[N], tt, n;
vector<int> G[N];

void dfs(int u) {
    visited[u] = 1;
    discovery[u] = ++tt;
    for (int i = 0; i < G[u].size(); i++) {
        if (visited[G[u][i]] == 0) {
            dfs(G[u][i]);
        }
    }
    finish[u] = ++tt;
}

int main() {
    int u, k, v;

    cin >> n;

    for (int i = 0; i < n; i++) {
        cin >> u >> k;
        u--;
        for (int j = 0; j < k; j++) {
            cin >> v;
            v--;
            G[u].push_back(v);
        }
    }
    memset(visited, 0, sizeof(visited));
    tt = 0;

    for (int i = 0; i < n; i++) {
        if (visited[i] == 0) {
            dfs(i);
        }
    }

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

    return 0;
}

C++: #include<iostream>
#include<vector>
#include<algorithm>
#include<cstdio>
#include<cstdlib>
#include<string>
#include<sstream>
#include<cmath>
#include<numeric>
#include<map>
#include<stack>
#include<queue>
using namespace std;
int inf = 1000000000;

class Graph{
public:
  int v;
  int ftime = -1;
  int ltime = -1;
  vector<int> e;
};
vector<Graph> g;
int cnt = 0;
void dfs(int pos){
  if( g[pos].ftime != -1 ) return;
  cnt++;
  g[pos].ftime = cnt;
  for(int i=0; i<g[pos].e.size(); i++){
    dfs(g[pos].e[i]);
  }
  cnt++;
  g[pos].ltime = cnt;
}

int main(void) {

  int n;
  cin >> n;
  g.resize(n);
  int u, k;
  for(int i=0; i<n; i++){
    cin >> u >> k;
    u--;
    g[u].v = u;
    g[u].e.resize(k);
    for(int j=0; j<k; j++){
      cin >> g[u].e[j];
      g[u].e[j]--;
    }
    sort(g[u].e.begin(), g[u].e.end());
  }
  for(int i=0; i<n; i++) dfs(i);
  for(int i=0; i<n; i++){
    cout << g[i].v + 1 << " " << g[i].ftime << " " << g[i].ltime << endl;
  }



  return 0;
}

// EOF