C++实现四则运算器(带括号)

基本分析可以看另一篇文章C++实现四则运算器(无括号)

栈的实现

//stack.h
#ifndef STACK_H
#define STACK_H
#include<iostream>
class stack_int
{
private:
	int* bottom;          //栈底
	int* top;             //栈顶
	unsigned int capacity;//栈容量
	unsigned int size;    //栈大小
public:
	stack_int() :bottom(new int[11]), top(bottom), capacity(10), size(0) {};
	stack_int(unsigned int capacity) :bottom(new int[capacity+1]),top(bottom), capacity(capacity),size(0){};
	int operator[](unsigned int i) const
	{
		return *(bottom + i);
	}
	bool isEmpty()const { return bottom == top; }
	bool isFull()const { return size == capacity-1; }
	unsigned int getsize()const { return size; }
	unsigned int getcapacity()const { return capacity; }
	int gettop()const
	{
		if (!isEmpty())
			return *(top - 1);
		else
			return -1;
	}
	void settop(int i)
	{
		if (!isEmpty())
		{
			*(top - 1) = i;
		}
	}
	void push(int i)
	{
		if ((top - bottom)<capacity)
		{
			*top = i;
			top++;
			size++;
		}
		else
		{
			std::cout << "stack full!" << std::endl;
			stack_expansion();
			push(i);
		}
	}
	int pop(int &val)
	{//返回值为1则栈未空，返回值为0则栈已空无法出栈
		if (top > bottom)
		{
			top--;
			size--;
			val = *top;
			return 1;
		}
		else
		{
			std::cout << "stack empty!" << std::endl;
			return NULL;
		}
	}
private:
	void stack_expansion()
	{//栈扩容
		std::cout << "正在扩容中..." << std::endl;
		int newcapacity = 2 * capacity + 1;
		int* newbottom = new int[newcapacity + 1];
		int* newtop = newbottom;
		for (int i = 0; i < size; ++i)
		{
			*newtop = *bottom;
			newtop++;
			bottom++;
		}
		bottom = newbottom;
		top = newtop;
		capacity = newcapacity;
	}
};

#endif

主程序

//Main.c
#include"stack.h"
#include<iostream>
using namespace std;
bool is_digit(char i)
{//是数字
	if (i == '1' || i == '2' || i == '3' || i == '4' || i == '5' || i == '6' || i == '7' || i == '8' || i == '9' || i == '0')
		return true;
	else return false;
}
bool is_operator(char i)
{//是运算符
	if (i == '+' || i == '-' || i == '*' || i == '/' || i == '(' || i == ')'||i=='=')
		return true;
	else return false;
}
bool get_priority(char pre,char cur)
{//获取两个符号间的优先级,pre为靠前的字符，cur为靠后的字符
	if ((pre == '+' || pre == '-') && (cur == '*' || cur == '/'))
		return false;
	else if (pre == '(' || cur == '(')
		return false;
	else
		return true;
}
int do_operation(int lnum, char ope, int rnum)
{
	if (ope == '+')
		return lnum + rnum;
	if (ope == '-')
		return lnum - rnum;
	if (ope == '*')
		return lnum * rnum;
	if (ope == '/')
		return lnum / rnum;
}
/*
1+2*3=
1*(2+1*(3+5)+4*3)=
先乘除，后加减，有括号先算括号内的
1+5*4-345+36/6*4+145*4*5-52=
*/

void do_arithmetic()
{
	stack_int s;
	stack_int num_stack;//数据栈
	stack_int ope_stack;//符号栈
	char current_char;
	current_char = getchar();
	bool overflag = false;//结束标志
	bool errorflag = false;//出错标志
	while (overflag != true)
	{//未遇到=号时不断进行四则运算
		if (is_digit(current_char))
		{//遇到数字符号则将完整的数解析出来并保存于栈中
			int num = 0;
			num = current_char - '0';//符号转数字
			current_char = getchar();//获取下一个字符
			while (is_digit(current_char))
			{
				num = num * 10 + (current_char - '0');
				current_char = getchar();
			}
			num_stack.push(num);
			//cout <<"the number is " <<num << endl;
		}
		if (current_char == ' '||current_char=='
')
		{//空格或换行则继续
			current_char = getchar();
			continue;
		}
		if (is_operator(current_char))
		{//遇到运算符则将运算符保存于运算符栈中
			int ope = '?';
			//如果当前符号栈非空，则不断根据优先级决定是否进行一次运算
			while ((!ope_stack.isEmpty()) && (get_priority((char)ope_stack.gettop(), current_char)))
			{//如果前一个运算符优先级更高
				ope_stack.pop(ope);
				//cout << "找到了前一个运算符为: " << (char)ope << endl;
				int lnum, rnum;
				//符号栈非空时，数据栈应该至少有两个数，否则出错
				if (num_stack.isEmpty())
				{
					cout << "error: 数据栈缺失两个元素，解析失败！" << endl;
					errorflag = true;
					overflag = true;
					break;
				}
				num_stack.pop(rnum);
				if (num_stack.isEmpty())
				{
					cout << "error: 数据栈缺失一个元素，解析失败！" << endl;
					errorflag = true;
					overflag = true;
					break;
				}
				num_stack.pop(lnum);
				lnum = do_operation(lnum, (char)ope, rnum);//进行运算
				num_stack.push(lnum);
			}
			if (current_char == '=')
			{//如果解析到=号了,解析完成
				if (!ope_stack.isEmpty())
				{
					errorflag = true;
					cout << "error: 缺失)" << endl;
				}
				overflag = true;
				break;
			}
			ope_stack.push(current_char);
			if (current_char == ')')
			{//右括号则出栈两次，将右括号和匹配的左括号出栈
				ope_stack.pop(ope);
				if (ope_stack.isEmpty())
				{
					cout << "error: 没有与)相匹配的(" << endl;
					errorflag = true;
					overflag = true;
					break;
				}
				ope_stack.pop(ope);
			}
			current_char = getchar();
		}
	}
	//for (int i = 0; i < num_stack.getsize(); ++i)
	//	cout << num_stack[i] << "	";
	//cout << endl;
	//for (int i = 0; i < ope_stack.getsize(); ++i)
	//	cout << (char)ope_stack[i] << "	";
	if (!errorflag)
		cout << num_stack.gettop() << endl;
}

int main()
{
	cout << " ______________" << endl;
	cout << "|整数四则运算器|" << endl;
	cout << " --------------" << endl;
	cout << "功能介绍：进行整数表达式的四则运算" << endl;
	cout << "可以使用的运算符:+ - * /" << endl;
	cout << "使用方式:输入以=结尾的算数运算表达式,回车后即可得到运算结果" << endl;
	cout << endl;
	//2432+5423-534*42=
	while (true)
	{
		cout << "____________________" << endl;
		cout << "--------------------" << endl;
		cout << "> ";
		do_arithmetic();
	}
	return 0;
}

程序大部分与不带括号版本很相似，主要更改了两个方面：

1.对于左括号，令左括号左边运算符优先级低于左括号，右边运算符优先级高于左括号(即，只要含有左括号的比较结果均为无法进行运算，函数get_priority返回值永远为false)。

2.对于右括号，令右括号左边的运算符(除左括号外)优先级均高于右括号，并且当右括号左边的符号为左括号时，两个括号相抵消，左括号退栈。

遇到右括号时，两括号内的+-*/运算全部可以进行，直到符号栈栈顶为左括号。