unique_ptr

Lab C++ Intermediate 20 points

Create a class Resource that prints acquire NAME in its constructor and release NAME in its destructor. For each input name, create it with make_unique inside a block, print using NAME, and let the block end.

Input

n, then n names.

Output

The event trace.

Example

Input

2
file
socket

Output

acquire file
using file
release file
acquire socket
using socket
release socket

Sample input available Sample output available

Editor

C++

Hints

A unique_ptr deletes its object automatically when it goes out of scope.

Solution explanation

This is RAII: tie a resource's lifetime to an object so cleanup can't be forgotten.

Show solution

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

class Resource {
public:
    explicit Resource(string name) : name_(name) { cout << "acquire " << name_ << "\n"; }
    ~Resource() { cout << "release " << name_ << "\n"; }
    const string &name() const { return name_; }

private:
    string name_;
};

int main() {
    int n;
    cin >> n;
    for (int i = 0; i < n; i++) {
        string name;
        cin >> name;
        {
            auto r = make_unique<Resource>(name);
            cout << "using " << r->name() << "\n";
        }
    }
    return 0;
}

Output

Answer