postexp.h

包含各种测试,查找和算法等代码,如冒泡算法,树的遍历,链表,队列,堆栈等

#include "LinStack.h"

template <class T> class PostExp
{
	private:
		LinStack<T> s;
		void Enter(T num);
		int GetTwoOperands(T& operand1, T& operand2);
		void Compute(char op);
	public:
		PostExp(void){};
		void Run(void);
		void Clear(void);
};

template <class T>
void PostExp<T>::Enter(T num)
{
	s.Push(num);
}

template <class T>
int PostExp<T>::GetTwoOperands(T& operand1, T& operand2)
{
	if(s.StackEmpty())
	{
		cerr << "缺少操作数!" << endl;
		return 0;
	}
	operand1 = s.Pop();
	if(s.StackEmpty())
	{
		cerr << "缺少操作数!" << endl;
		return 0;
	}
	operand2 = s.Pop();
	return 1;
}

template <class T>
void PostExp<T>::Compute(char op)
{
	int result;
	T operand1, operand2;
	result = GetTwoOperands(operand1, operand2);
	if(result = 1)
		switch(op)
		{
			case '+':	s.Push(operand2 + operand1);
						break;
			case '-':	s.Push(operand2 - operand1);
						break;
			case '*':	s.Push(operand2 * operand1);
						break;
			case '/':	s.Push(operand2 / operand1);
						break;
	}
	else 
		s.ClearStack();
}

template <class T>
void PostExp<T>::Run(void)
{
	char c;
	T newOperand;

	cout << "输入后缀表达式, 以#号结束:" << endl;
	while(cin >> c, c != '#')
	{
		switch(c)
		{
			case '+':
			case '-':
			case '*':
			case '/':	Compute(c);
						break;
			default:	cin.putback(c);
						cin >> newOperand;
						Enter(newOperand);
						break;
		}
	}
	if(!s.StackEmpty())
		cout << s.Peek() << endl;
}

template <class T>
void PostExp<T>::Clear(void)
{
	s.ClearStack();
}