本文实例为大家分享了C++实现简单计算器的具体代码，供大家参考，具体内容如下
工具
- stack
- map
步骤
- 初始化
- 读取字符串
- 去空格
- 负号处理
- 判断为空
- 检查格式
- 计算
示例
代码
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#include <iostream>#include <string>#include <stdio.h>#include <stack>#include <map>#include <math.h>#include <stdlib.h>#include <sstream>using namespace std;char op[8][8];map<char, int> m;void init(){ m['+'] = 1, m['-'] = 2, m['*'] = 3, m['/'] = 4, m['('] = 5, m[')'] = 6, m['#'] = 7; op[1][1] = '>', op[1][2] = '>', op[1][3] = '<', op[1][4] = '<', op[1][5] = '<', op[1][6] = '>', op[1][7] = '>'; op[2][1] = '>', op[2][2] = '>', op[2][3] = '<', op[2][4] = '<', op[2][5] = '<', op[2][6] = '>', op[2][7] = '>'; op[3][1] = '>', op[3][2] = '>', op[3][3] = '>', op[3][4] = '>', op[3][5] = '<', op[3][6] = '>', op[3][7] = '>'; op[4][1] = '>', op[4][2] = '>', op[4][3] = '>', op[4][4] = '>', op[4][5] = '<', op[4][6] = '>', op[4][7] = '>'; op[5][1] = '<', op[5][2] = '<', op[5][3] = '<', op[5][4] = '<', op[5][5] = '<', op[5][6] = '='; op[6][1] = '>', op[6][2] = '>', op[6][3] = '>', op[6][4] = '>', op[6][6] = '>', op[6][7] = '>'; op[7][1] = '<', op[7][2] = '<', op[7][3] = '<', op[7][4] = '<', op[7][5] = '<', op[7][7] = '=';}double operate(double num1, char oper, double num2){ if(oper == '+') return num1 + num2; if(oper == '-') return num1 - num2; if(oper == '*') return num1 * num2; if(oper =='/') return num1 / num2;}string trim(string str){ index = 0; if(!str.empty()){ while((index = str.find(' ',index) != string::nops) str.erase(index,1); } return str;}string change(string str){ int start; start += "#"; for(int i = 0; i < str.length(); i++){ if(str[i] == '-'){ if(i == 0 || i != 0 && (m[str[i-1]] >= 1 && m[str[i-1]] <= 5 && str[i+1] >= '0' && str[i+1] <= '9'){ str += " "; int j = i+1; start = j; while(m[str[j]] == 0) j++; for(int k = str.length() - 1; k >= j; k--) str[k] = str[k-3]; str[i] = '(', str[i+1] = '0', str[i+2] = '-'; int l = i+3; string s = str.substr(start, j - start); for(int k = 0; k < s.length(); k++) str[l+k] = s[k]; str[l+s.length()] = ')'; } } } str.erase(str.length()-1, 1); return str;}bool test(string str){ bool ifOK = true; int flag = 0; stack<char> s; int start, e; str += "#"; for(int i = 0; i < str.length(); i++){ //判断非法字符 if((str[i] < '0' || str[i] > '9') && m[str[i]] == 0 && str[i] != '.') return false; if(str[i] == '#' && i!= str.length()-1) return false; //判断小数点 if(m[str[i]] == 0){ if(flag == 0){ start = i; flag = 1; } } if(m[str[i]] != 0){ if(flag == 1){ e = i; string st = str.substr(start, e - start); int pointNum = 0; if(st[0] == '.') return false; for(int j = 0; j < st.length(); j++){ if(st[j] == '.') pointNum++; } if(pointNum > 1) return false; } flag = 0; } //判断运算符 if(str[i] == '+' || str[i] == '-' || str[i] == '*' || str[i] == '/'){ if(i == 0) return false; if((str[i-1] < '0' || str[i-1] > '9') && str[i-1] != ')') return false; if((str[i+1] < '0' || str[i+1] > '9') && str[i+1] != '(') return false; } //判断括号 if(str[i] == '(') s.push(str[i]); if(str[i] == ')'){ if(s.empty()) return false; char c = s.top(); if(c == '(') s.pop(); else return false; } } //判断括号 if(!s.empty()) ifOK = false; return ifOK;}void caculate(string str){ str += "#"; int flag = 0; int start, e; stack<double> numStack;//操作数栈 stack<char> operStack;//运算符栈 operStack.push('#'); int i = 0; while(str[i] != '#' || operStack.top() != '#'){ if(m[str[i]] == 0){ if(flag == 0){ start = i; flag = 1; } } else{ if(flag == 1){ e = i; //string 转 double stringstream s (str.substr(start, e - start)); double num; s >> num; numStack.push(num); flag = 0; } char c = operStack.top; if(op[m[c]][m[str[i]]] == '<'){ operStack.push(str[i]); i++; } else if(op[m[c]][m[str[i]]] == '='){ operStac.pop(); i++; } else{ char oper = operStack.top(); operStac.pop(); double num2 = numStack.top(); numStack.pop(); double num1 = numStack.top(); numStack.pop(); double result = operate(num1, oper, num2); numStack.push(result); } } } printf("\t\t\t= %f\n",numStack.top()); }int main(){ init();//初始化 printf("\n\n\n\t\t\t请输入表达式， 退出请输入end：\n"); string s; getline(cin, s, "\n");//读取字符串 s = trim(s);//去空格 s = change(s);//处理负号 if(s == "end"){ break; } else if(s.length() > 0){//判断为空 if(!test(s))//检查格式 printf("\t\t\t格式错误\n"); else caculate(s);//计算 } else{ printf("\t\t\t输入不能为空\n"); }} |
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原文链接：https://blog.csdn.net/weixin_43673669/article/details/86667243
