C++实现简单计算器实验报告（C++实现计算器）

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

C++实现简单计算器实验报告（C++实现计算器）

代码

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 #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"); } }