Language: C++

#include <iostream>
#include <vector>
#include <vector>
#include <algorithm>
#include <stack>

using namespace std;

static const int N = 100;
int n, m[N][N];
int time, begT[N], endT[N];
bool visited[N];

int nxt(int u)
{
	for (int v = 0; v < n; ++v)
	{
		if (m[u][v] > 0 && !visited[v]) return v;
	}
	return -1;
}

void dfs_helper(int idx)
{
	stack<int> s;
	s.push(idx);
	begT[idx] = time++;
	visited[idx] = true;

	while (!s.empty())
	{
		int u = s.top();
		int v = nxt(u);
		if (-1 == v)
		{
			s.pop();
			endT[u] = time++;
			continue;
		}
		s.push(v);
		begT[v] = time++;
		visited[v] = true;
	}
}

void dfs()
{
	time = 1;

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

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

int main()
{
	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)
		visited[i] = false;

	for (int i = 0; i < n; ++i) {
		int u, d;
		cin >> u >> d;
		for (int j = 0; j < d; ++j)	{
			int v; cin >> v;
			m[u - 1][v - 1] = 1;
		}
	}

	dfs();

	return 0;
}

Compiler output:
a.cc:11:5: error: 'int time' redeclared as different kind of entity
   11 | int time, begT[N], endT[N];
      |     ^~~~
In file included from /usr/include/pthread.h:23,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/gthr-default.h:35,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/gthr.h:157,
                 from /usr/include/c++/14/ext/atomicity.h:35,
                 from /usr/include/c++/14/bits/ios_base.h:39,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/time.h:76:15: note: previous declaration 'time_t time(time_t*)'
   76 | extern time_t time (time_t *__timer) __THROW;
      |               ^~~~
a.cc: In function 'void dfs_helper(int)':
a.cc:27:21: warning: ISO C++ forbids incrementing a pointer of type 'time_t (*)(time_t*) noexcept' {aka 'long int (*)(long int*) noexcept'} [-Wpointer-arith]
   27 |         begT[idx] = time++;
      |                     ^~~~
a.cc:27:25: error: lvalue required as increment operand
   27 |         begT[idx] = time++;
      |                         ^~
a.cc:37:35: warning: ISO C++ forbids incrementing a pointer of type 'time_t (*)(time_t*) noexcept' {aka 'long int (*)(long int*) noexcept'} [-Wpointer-arith]
   37 |                         endT[u] = time++;
      |                                   ^~~~
a.cc:37:39: error: lvalue required as increment operand
   37 |                         endT[u] = time++;
      |                                       ^~
a.cc:41:27: warning: ISO C++ forbids incrementing a pointer of type 'time_t (*)(time_t*) noexcept' {aka 'long int (*)(long int*) noexcept'} [-Wpointer-arith]
   41 |                 begT[v] = time++;
      |                           ^~~~
a.cc:41:31: error: lvalue required as increment operand
   41 |                 begT[v] = time++;
      |                               ^~
a.cc: In function 'void dfs()':
a.cc:48:14: error: assignment of function 'time_t time(time_t*)'
   48 |         time = 1;
      |         ~~~~~^~~