C++实现四则运算器（带括号）

本文实例为大家分享了C++实现四则运算器的具体代码，供大家参考，具体内容如下

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
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) 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
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;
}


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 " < ";
 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。

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持考高分网。