exam3.cpp

来自「C++语言程序设计题典」· C++ 代码 · 共 149 行

#include <iostream.h>
#include <math.h>
#include <string.h>
#include <stdlib.h>
const int Max=20;
class Stack
{
	double stack[Max];
	int top;
public:
	Stack() { top=-1; }
	void push(double d)
	{
		if (top==Max-1)
		{
			cout << "栈上溢出" << endl;
			return;
		}
		top++;
		stack[top]=d;
	}
	double pop()
	{
		double temp;
		if (top==-1)
		{
			cout << "栈下溢出" << endl;
			exit(1);
		}
		temp=stack[top];
		top--;
		return temp;
	}
	void clear()
	{
		top=-1;
	}
	double peek()
	{
		if (top==-1)
		{
			cout << "栈下溢出" << endl;
			exit(1);
		}
		return stack[top];
	}
	int empty()
	{
		return (top==-1);
	}
	int full()
	{
		return (top==Max-1);
	}
};
class Calc
{
	Stack S;
	void enter(double d)
	{
		S.push(d);
	}
	int gettwodata(double &op1,double &op2)
	{
		if (S.empty())
		{
			cout << "没有操作数" << endl;
			return 0;
		}
		op1=S.pop();
		if (S.empty())
		{
			cout << "操作数不够" << endl;
			return 0;
		}
		op2=S.pop();
		return 1;
	}
	void computer(char op)
	{
		int result;
		double op1,op2;
		result=gettwodata(op1,op2);
		if (result==1)
		{
			switch(op)
			{
			case '+':S.push(op2+op1);
			         break;
			case '-':S.push(op2-op1);
				     break;
			case '*':S.push(op2*op1);
				     break;
			case '/':if (op1==0)
					 {
						 cout << "除零错误" << endl;
						 S.clear();
					 }
				     else
					     S.push(op2/op1);
				     break;
			case '^':S.push(pow(op2,op1));
				     break;
			}
			cout << "   >>" << S.peek() << " ";
		}
		else
			S.clear();
	}
public:
	Calc() {};
	void run()
	{
		char c[20];
		while (1)
		{
			cin >> c;
			if (*c=='q') break;   //键入q表示退出
			switch (*c)
			{
            case 'c':S.clear();   //键入c表示从新开始计算
				     break;
            case '-':if (strlen(c)>1)
			            enter(atof(c));
				     else
						 computer(*c);
					 break;
			case '+':
			case '*':
			case '/':
			case '^':computer(*c);
			         break;
			default:enter(atof(c));
				break;
			}
		}
	}
	void clear()
	{
		S.clear();
	}
};
void main()
{
	cout << "输入后缀表达式(数,符号,数之间空一格):\n   >>";
	Calc c;
	c.run();
}