stack.cpp

包括图、二叉树、链表

#include "Stack.h"
Error_code Stack::push(const Stack_entry &item)
/*
Pre:  None.
Post: If the Stack is not full, item is added to the top
of the Stack.  If the Stack is full,
an Error_code of overflow is returned and the Stack is left unchanged.
*/

{
	Error_code outcome = success;
	if (count >= maxstack)
		outcome = overflow;
	else
		entry[count++] = item;
	return outcome;
}


Error_code Stack::pop()
/*
Pre:  None.
Post: If the Stack is not empty, the top of
the Stack is removed.  If the Stack
is empty, an Error_code of underflow is returned.
*/

{
	Error_code outcome = success;
	if (count == 0)
		outcome = underflow;
	else --count;
	return outcome;
}


Error_code Stack::top(Stack_entry &item) const
/*
Pre:  None.
Post: If the Stack is not empty, the top of
the Stack is returned in item.  If the Stack
is empty an Error_code of underflow is returned.
*/

{
	Error_code outcome = success;
	if (count == 0)
		outcome = underflow;
	else
		item = entry[count - 1];
	return outcome;
}


bool Stack::empty() const
/*
Pre:  None.
Post: If the Stack is empty, true is returned.
Otherwise false is returned.
*/

{
	bool outcome = true;
	if (count > 0) outcome = false;
	return outcome;
}

Stack::Stack()
/*
Pre:  None.
Post: The stack is initialized to be empty.
*/
{
	count = 0;
}
void Stack::clear()
{
	count = 0;
}

bool Stack::full() const
{
	return count==maxstack;
}
int Stack::size() const
{
	return count;	
}