Go: package main

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

var scanner = bufio.NewScanner(os.Stdin)

func nextString() string {
	scanner.Scan()
	return scanner.Text()
}

func nextInt() int {
	n, err := strconv.Atoi(nextString())
	if err != nil {
		fmt.Printf("strconv.Atoi failed: %v\n", err)
	}
	return n
}

var infty = 1000000000

type nodeKey int

type DirectedGraphNode struct {
	key       nodeKey
	adjacents []*DirectedGraphNode
	visited   bool
	d         int
	f         int
	parent    *DirectedGraphNode
}

type DirectedGraph struct {
	nodes []*DirectedGraphNode
}

func (g *DirectedGraph) setAdjacency(l, r nodeKey) {
	g.nodes[l].adjacents = append(g.nodes[l].adjacents, g.nodes[r])
}

func newDirectedGraph(nNodes int) *DirectedGraph {
	graph := DirectedGraph{}
	graph.nodes = make([]*DirectedGraphNode, nNodes)
	for iNodes := 0; iNodes < nNodes; iNodes++ {
		graph.nodes[iNodes] = &DirectedGraphNode{}
		graph.nodes[iNodes].key = nodeKey(iNodes)

		graph.nodes[iNodes].visited = false
		graph.nodes[iNodes].d = infty
		graph.nodes[iNodes].f = infty
		graph.nodes[iNodes].parent = nil
	}
	return &graph
}

type QueueEntry struct {
	node *DirectedGraphNode
	next *QueueEntry
}

type Queue struct {
	head, tail *QueueEntry
}

func (q *Queue) enqueue(node *DirectedGraphNode) {
	entry := QueueEntry{}
	entry.node = node

	if q.tail == nil {
		q.head = &entry
		q.tail = &entry
		return
	}

	q.tail.next = &entry
	q.tail = q.tail.next
}

func (q *Queue) dequeue() *QueueEntry {
	if q.head == nil {
		return nil
	}
	poped := q.head
	q.head = q.head.next
	if q.head == nil {
		q.tail = nil
	}
	return poped
}

func (q *Queue) isEmpty() bool {
	return q.head == nil
}

var time = 0

func fillDistancesByDepthFirstSearch(g *DirectedGraph) {
	for _, u := range g.nodes[1:] {
		if !u.visited {
			dfsVisit(g, u)
		}
	}
}

func dfsVisit(g *DirectedGraph, u *DirectedGraphNode) {
	time++
	u.d = time

	u.visited = true
	for _, v := range u.adjacents {
		if !v.visited {
			v.parent = u
			dfsVisit(g, v)
		}
	}
	time++
	u.f = time
}

func main() {
	scanner.Split(bufio.ScanWords)

	nNodes := nextInt()
	g := newDirectedGraph(nNodes + 1)

	for iNode := 0; iNode < nNodes; iNode++ {
		nodeKeyLeft := nodeKey(nextInt())
		nAdj := nextInt()
		for iAdj := 0; iAdj < nAdj; iAdj++ {
			nodeKeyRight := nodeKey(nextInt())
			g.setAdjacency(nodeKeyLeft, nodeKeyRight)
		}
	}

	fillDistancesByDepthFirstSearch(g)

	for iNode := 1; iNode <= nNodes; iNode++ {
		node := g.nodes[iNode]
		fmt.Println(node.key, node.d, node.f)
	}
}

Python: #!/usr/bin/env python3
# -*- coding: utf-8 -*-

import sys

WHITE = 0
GRAY = 1
BLACK = 2


def dbg_record(records):
    for index, record in enumerate(records):
        print("???????????????: %d" % index)
        if isinstance(record, dict):
            print("??\??????: %d" % record.get("visit", -1))
            print("?????????: %d" % record.get("leave", -1))
        else:
            print("?????????")
        print("")


def dfs(matrix):
    def internal_dfs(node_id, current_time):
        if state[node_id] == WHITE:
            # ?¨??????????
            state[node_id] = GRAY
            stack.append(node_id)
            records[node_id] = {"visit": current_time}  # ?¨??????????????¨????

            # ?¬?????¨????????????¨?????§????????????????????¢???
            next_id = None
            for index in range(len(matrix)):
                if matrix[node_id][index] == 1 and state[index] == WHITE:
                    next_id = index
                    break

            if next_id is not None:
                internal_dfs(next_id, current_time + 1)
            elif 0 < len(stack):
                # ?¬?????¨????????????¨?????§?????????????????????????????????????????°?????????
                internal_dfs(stack.pop(), current_time + 1)
        elif state[node_id] == GRAY:
            # ????????????
            state[node_id] = BLACK
            records[node_id]["leave"] = current_time  # ????????????????¨????

            # ?¬?????¨????????????¨?????§????????????????????¢???
            next_id = None
            for index in range(len(matrix)):
                if matrix[node_id][index] == 1 and state[index] == WHITE:
                    next_id = index
                    break

            if next_id is not None:
                internal_dfs(next_id, current_time + 1)
            elif 0 < len(stack):
                # ?¬?????¨????????????¨?????§?????????????????????????????????????????°?????????
                internal_dfs(stack.pop(), current_time + 1)

    state = [WHITE] * len(matrix)  # White, Gray, Black
    records = [None] * len(matrix)  # Save time when the node is processed
    stack = []

    internal_dfs(0, 1)
    # dbg_record(records)
    return records


if __name__ == "__main__":
    # ??????????????????
    lines = [
        "6",
        "1 2 2 3",
        "2 2 3 4",
        "3 1 5",
        "4 1 6",
        "5 1 6",
        "6 0",
    ]
    # lines = sys.stdin.readlines()

    # Create n * n matrix
    dimension = int(lines[0])
    matrix = []
    for x in range(dimension):
        matrix.append([0] * dimension)

    # Set edge info
    for index, line in enumerate(lines[1:]):
        for edge in [int(x) for x in line.strip().split(" ")[2:]]:
            matrix[index][edge - 1] = 1

    result = dfs(matrix)
    for index, line in enumerate(result):
        print("%d %d %d" % (index + 1, line["visit"], line["leave"]))

Python: # 深さ優先探索（行きがけ、帰りがけ）
import sys
input = sys.stdin.readline
from collections import deque

# グラフの作成(無向グラフでは#を消す)
N = int(input())
graph = [deque([]) for _ in range(N + 1)]
for _ in range(N):
    u, k, * v = [int(x) for x in input().split()] # uは頂点番号、kは隣接頂点の個数
    v.sort()
    for i in v:
        graph[u].append(i)
        # graph[i].append(u) # 無向グラフ

time = 0
arrive_time = [-1] * (N + 1) # 到着時刻
finish_time = [-1] * (N + 1) # 探索終了時刻

# 深さ優先探索
def dfs(v):
    global time
    time += 1
    stack = [v]
    arrive_time[v] = time
    while stack:
        v = stack[-1]
        if graph[v]:
            w = graph[v].popleft()
            if arrive_time[w] < 0:
                time += 1
                arrive_time[w] = time
                stack.append(w) 
        else:
            time += 1
            finish_time[v] = time
            stack.pop()          
    return [arrive_time, finish_time]

# 孤立している頂点対策
for i in range(N):
    if arrive_time[i + 1] < 0:
        ans = dfs(i + 1)

# 頂点番号、到着時刻、終了時刻
for j in range(N):
    temp = [j + 1, ans[0][j + 1], ans[1][j + 1]]
    print(* temp)

Python: # Depth First Search
from collections import deque

N = int(input())
nodes = []
G ={}
is_visited = {}

for _ in range(N):
    lst = list(map(int, input().split()))
    idx = lst[0]
    nodes.append(idx)
    is_visited[idx] = False
    degree = lst[1]
    if degree > 0:
        G[idx] = lst[2:]
    else:
        G[idx] = []
        
d = {}  # 最初に訪問したときの発見時刻を記録する
f = {}  # 隣接リストを調べ終えた完了時刻を記録する
t = 1

def dfs(node):
    global t
    if (is_visited[node] == True):
        return
    is_visited[node] = True
    d[node] = t
    t += 1  # 時刻を一つ進める
    # 再帰探索
    for idx in G[node]:
        dfs(idx)
    f[node] = t
    t += 1  # 関数を終了するときにも+1する


for node in nodes:  # 孤立しているノードもあるためこうして対処
    dfs(node)

for node in nodes:
    print(node, d[node], f[node])

Python: def dfs(i,cnt):
    d[i] = cnt
    cnt += 1
    for j in edge[i]:
        if d[j] == -1:
            cnt = dfs(j,cnt)
    f[i] = cnt
    cnt += 1
    return cnt

n = int(input())
edge = [[] for i in range(n)]
for not_used in range(n):
    of_children, not_used, *v = map(lambda x: int(x)-1,input().split())
    edge[of_children] = sorted(v)
c = 1
d = [-1]*n
f = [-1]*n

for i in range(n):
    if d[i] == -1:
        c = dfs(i,c)
for i ,(d,f) in enumerate(zip(d,f)):
    print(i+1,d,f)