#include <iostream>

template <typename T>
class MyVector {
public:
    MyVector() : _data(nullptr), _size(0), capacity(0) {}

    ~MyVector() {
        delete[] _data;
    }

    void push_back(const T& value) {
        if (_size == capacity) {
            resize();
        }
        _data[_size++] = value;
    }

    void pop_back() {
        if (_size > 0) {
            --_size;
        }
    }

    T& operator[](size_t index) {
        return _data[index];
    }

    const T& operator[](size_t index) const {
        return _data[index];
    }

    size_t size() const {
        return _size;
    }

private:
    T* _data;
    size_t _size;
    size_t capacity;

    void resize() {
        capacity = capacity == 0 ? 1 : capacity * 2;
        T* new_data = new T[capacity];
        for (size_t i = 0; i < _size; ++i) {
            new_data[i] = _data[i];
            // delete &_data[i];
        }
        delete[] _data;
        _data = new_data;
    }
};

int main() {
    MyVector<int> v;
    std::cout << "add fist" << std::endl;
    v.push_back(35);

    for (size_t i = 0; i < v.size(); ++i) {
        std::cout << "value: " << v[i] << ", address: " << &v[i] << std::endl;
    }

    std::cout << "add second" << std::endl;
    v.push_back(30);

    for (size_t i = 0; i < v.size(); ++i) {
        std::cout << "value: " << v[i] << ", address: " << &v[i] << std::endl;
    }

    std::cout << "add third" << std::endl;
    v.push_back(25);

    for (size_t i = 0; i < v.size(); ++i) {
        std::cout << "value: " << v[i] << ", address: " << &v[i] << std::endl;
    }

    std::cout << "Pop Back" << std::endl;

    v.pop_back();

    for (size_t i = 0; i < v.size(); ++i) {
        std::cout << "value: " << v[i] << ", address: " << &v[i] << std::endl;
    }

    std::cout << "add Fourth" << std::endl;
    v.push_back(20);

    for (size_t i = 0; i < v.size(); ++i) {
        std::cout << "value: " << v[i] << ", address: " << &v[i] << std::endl;
    }
    std::cout << std::endl;

    return 0;
}
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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
}