Challenge: Enter and Leave

Lab C++ Beginner 10 points

Write a class Room whose constructor prints enter NAME and whose destructor prints leave NAME. Read n names. Create the rooms nested: each one inside the one before, by having a recursive function create one Room and then call itself for the next name.

Input

n, then n names.

Output

For 2 names a b: enter a, enter b, leave b, leave a, one per line.

Example

Input

2
a b

Output

enter a
enter b
leave b
leave a

Sample input available Sample output available

Editor

C++

Hints

The destructor's name is ~Room().

visit(names, i) makes Room r(names[i]); then calls visit(names, i + 1);

Each Room is destroyed when its visit() call ends, so they leave in reverse order.

Solution explanation

Each call keeps its Room alive until the deeper calls finish, so destructors run in reverse order – exactly how RAII cleans up.

Show solution

#include <iostream>
#include <string>
#include <vector>
using namespace std;

class Room {
    string name;
public:
    Room(string n) : name(n) { cout << "enter " << name << "\n"; }
    ~Room() { cout << "leave " << name << "\n"; }
};

void visit(const vector<string>& names, int i) {
    if (i == static_cast<int>(names.size())) {
        return;
    }
    Room r(names[i]);
    visit(names, i + 1);
}

int main() {
    int n;
    cin >> n;
    vector<string> names(n);
    for (string& s : names) cin >> s;
    visit(names, 0);
    return 0;
}

Output

Answer