#include <iostream>
#include <memory>

class Resource {
public:
    Resource(int value) : data(value) {
        std::cout << "Resource acquired: " << data << std::endl;
    }
    ~Resource() {
        std::cout << "Resource destroyed: " << data << std::endl;
    }
    void use() {
        std::cout << "Using resource: " << data << std::endl;
    }
private:
    int data;
};

void uniquePtrExample() {
    std::cout << "unique_ptr example:" << std::endl;
    std::unique_ptr<Resource> uniqueRes = std::make_unique<Resource>(1);
    uniqueRes->use();
    // uniqueRes will be automatically deleted when it goes out of scope
}

void sharedPtrExample() {
    std::cout << "\nshared_ptr example:" << std::endl;
    std::shared_ptr<Resource> sharedRes1 = std::make_shared<Resource>(2);
    {
        std::shared_ptr<Resource> sharedRes2 = sharedRes1;
        std::cout << "Resource count: " << sharedRes1.use_count() << std::endl;
        sharedRes2->use();
    }
    std::cout << "Resource count after inner scope: " << sharedRes1.use_count() << std::endl;
    // sharedRes1 will be deleted when the last shared_ptr goes out of scope
}

void weakPtrExample() {
    std::cout << "\nweak_ptr example:" << std::endl;
    std::shared_ptr<Resource> sharedRes = std::make_shared<Resource>(3);
    std::weak_ptr<Resource> weakRes = sharedRes;
    
    if (auto tempShared = weakRes.lock()) {
        tempShared->use();
    } else {
        std::cout << "Resource no longer available" << std::endl;
    }
    
    sharedRes.reset();  // Explicitly release the resource
    
    if (auto tempShared = weakRes.lock()) {
        tempShared->use();
    } else {
        std::cout << "Resource no longer available" << std::endl;
    }
}

int main() {
    uniquePtrExample();
    sharedPtrExample();
    weakPtrExample();
    return 0;
}
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C++ Online Compiler

Write, Run & Share C++ code online using OneCompiler's C++ online compiler for free. It's one of the robust, feature-rich online compilers for C++ language, running on the latest version 17. Getting started with the OneCompiler's C++ compiler is simple and pretty fast. The editor shows sample boilerplate code when you choose language as C++ and start coding!

Read inputs from stdin

OneCompiler's C++ online compiler supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample program which takes name as input and print your name with hello.

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

int main() 
{
    string name;
    cout << "Enter name:";
    getline (cin, name);
    cout << "Hello " << name;
    return 0;
}

About C++

C++ is a widely used middle-level programming language.

  • Supports different platforms like Windows, various Linux flavours, MacOS etc
  • C++ supports OOPS concepts like Inheritance, Polymorphism, Encapsulation and Abstraction.
  • Case-sensitive
  • C++ is a compiler based language
  • C++ supports structured programming language
  • C++ provides alot of inbuilt functions and also supports dynamic memory allocation.
  • Like C, C++ also allows you to play with memory using Pointers.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition If-Else is used.

if(conditional-expression) {
   //code
}
else {
   //code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression){    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
......    
    
default:     
 code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  //code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while (condition) {  
// code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {  
 // code 
} while (condition);

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity. Function gets run only when it is called.

How to declare a Function:

return_type function_name(parameters);

How to call a Function:

function_name (parameters)

How to define a Function:

return_type function_name(parameters) {  
 // code
}