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
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//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
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//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=='\n') {//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] << "\t"; //cout << endl; //for (int i = 0; i < ope_stack.getsize(); ++i) // cout << (char)ope_stack[i] << "\t"; 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。
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服务器之家。
原文链接：https://blog.csdn.net/weixin_43972675/article/details/107837707
