8. destruct, construct, deep copy, shallow copy, assignment operator overload

OOP Implement a sequential stack

class SeqStack
{
    
public:
	// Constructors 
	// With parameters , So it can be overloaded , There are multiple constructors 
	SeqStack(int size = 10)
	{
    
		_pstack = new int[size];
		_top = -1;
		_size = size;
	}
	// Destructor 
	~SeqStack()
	{
    
		delete[] _pstack;
		_pstack = nullptr;
	}
	void push(int val)
	{
    
		if(full())
			resize();
		_pstack[++_top] = val;
	}
	void pop()
	{
    
		if(empty())
			return ;
		--_top;
	}
	int top()
	{
    
		return _pstack[_top];
	}
	bool empty()
	{
    
		return _top == -1;
	}
	bool full()
	{
    
		return _top == _size-1;
	}
private:
	int* _pstack;// Dynamic array , Storage order stack element 
	int _top;// Point to the position of the element at the top of the stack 
	int _size;// Total size of array expansion 
	void resize()
	{
    
		// According to the original 2 Double expansion 
		int* ptmp = new int[_size * 2];
		for(int i=0;i<_size;++i)
		{
    
			ptmp[i] = _pstack[i];
		}
		delete[] _pstack;
		_pstack = ptmp;
		_size *= 2;
	}
};

The construction order is opposite to the destruction order ！

Destructors can call themselves ：
s1.~SeqStack();
But after the call , The object doesn't exist ！ Therefore, it is not recommended to call destructors by yourself ！

that new Well ？
malloc Open up memory +SeqStack(60) Object construction ！

Parameters of member methods , The compiler will automatically add a this The pointer ！

The default copy constructor of an object is to copy data in memory ！ The key is if the object occupies external resources , Then shallow copy is a problem ！

// Custom copy constructor 
SeqStack(const SeqStack& src)
{
    
	_pstack = new int[src._size];
	for(int i=0,i<_top;i++)
	{
    
		_pstack[i] = src._pstack[i];
	}
	_top = src._top;
	_size = src._size;
}
// Assignment operator = heavy load 
void operator=(const SeqStack& src)
{
    
	if(this == &src)
		return;
	delete[] _pstack;
	_pstack = new int [src._size];
	for(int i=0;i<=src._top;++i)
	{
    
		_pstack[i] = src._pstack[i];
	}
	_top = src._top;
	_size = src._size;
}