用栈实现简易计算器c++

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//easy caculator // //Created by zzx on 2018.10.10 #include <iostream> using namespace std; #include <string> #include <stdlib.h> #define MaxSize 100 char precede(char a, char b); template <class T> class stack { private: int top; T data[MaxSize] = { 0 }; public: void intstack(stack <T> *s)//初始化栈 { s->top = 0; } int isEmpty(stack<T> *s)//判断栈空 { if (s->top == 0) { return 0; } return 1; } int isfull(stack <T> *s)//判断栈满 { if (s->top == MaxSize) return 0; return 1; } int push(stack <T> *s, T x)//进栈 { if (!isfull(s)) { return -1; } else { if (!isEmpty(s)) top = 0; s->top++; s->data[s->top - 1] = x; } return 0; } T pop(stack <T> *s)//栈顶元素出栈 { if (!isEmpty(s)) return -1; else { T x; x = s->data[s->top - 1]; s->top--; return x; } } T gettop(stack <T> *s)//取出栈顶元素 { if (!isEmpty(s)) return -1; else { T x; x = s->data[s->top - 1]; return x; } } }; /* 【函数名】calc 【函数功能】计算表达式 【参数】a被操作数 【参数】c运算符 【参数】b被操作数 */ double calc(double b, char c, double a) { double result; switch (c) { case '+': result = a + b; break; case '-': result = a - b; break; case '*': result = a * b; break; case '/': result = a / b; break; default: cout << "calc函数计算出错" << endl; return -1; } return result; } /* 【函数名】 解析表达式 【参数str[]】输入的字符串 【参数a】操作数栈地址 【参数b】运算符地址 */ int parse(char str[], stack <double> *a, stack <char> *b)//解析表达式 { char dou[MaxSize] = { 0 }; double result = 0; for (int i = 0; str[i] != ''; i++)//如果字符串不为''则继续循环 { char c = str[i]; if (c >= '0'&&c <= '9' || c == '.') { //处理操作数 char t[20] = { 0 };//建立个储存单个数据的数组 int j=0; for ( j = 0; str[i + j] >= '0'&&str[i + j] <= '9' || str[i + j] == '.'; j++) //遇到数据字符时提取后面字符直到遇到运算符 { t[j] = str[i + j]; } t[j] = ''; i = i + j - 1;//更新i double value = atof(t);//将字符串数组压缩为浮点型 (*a).push(a, value); } else { //处理运算符 if (!(*b).isEmpty(b))//判断是否为空 空为真 { (*b).push(b, c); } else { char op = 0; double num1 = 0; double num2 = 0; op = (*b).gettop(b);//取栈顶元素 op = precede(op, c); switch (op) { case '<':(*b).push(b, c); break;//优先级高于栈顶元素，直接入栈 case '=':(*b).pop(b); break;//弹出左括号 case '>'://退栈并进行计算将结果存放到操作数栈 //运算符继续进行比较 num1 = (*a).pop(a); num2 = (*a).pop(a); op = (*b).pop(b); result = calc(num1, op, num2); (*a).push(a, result); i--;//保证括号与其它运算符结合时正确 break; default: cout << "表达式解析出错,可能是输入了错误符号:(" << endl << endl; return -1; } } } } while ((*b).isEmpty(b)) { char op = 0; double num1 = 0; double num2 = 0; num1 = (*a).pop(a); num2 = (*a).pop(a); op = (*b).pop(b); result = calc(num1, op, num2); (*a).push(a, result); } if (!(*b).isEmpty(b)) result = (*a).pop(a); if (!(*a).isEmpty(a)) { cout << ":)表达式计算结果为(最多保存小数点后六位)：" << result << endl << endl; return 0; } cout << "erroring!\n"; } char precede(char a, char b)//比较运算符的优先级 { char prior_table[6][6] = {//按运算优先级制表 //+ - * / ( ) {'>','>','<','<','<','>'},//+加号 {'>','>','<','<','<','>'},//-减号 {'>','>','>','>','<','>'},//*乘号 {'>','>','>','>','<','>'},// /除号 {'<','<','<','<','<','='},// （左括号 { '>','>','>','>','>','>' }// ）右括号 }; int x = -1; int y = -1; char opr[] = "+-*/()"; for (int i = 0; i < 6; i++)//遍历二维数组查找对应的运算关系 { if (a == opr[i])x = i; if (b == opr[i])y = i; } return prior_table[x][y]; } int main() { while (1) { stack<double> num_stack; stack<char> str_stack;//将类模板的数据类型定义好 num_stack.intstack(&num_stack); str_stack.intstack(&str_stack); cout << "************************************" << endl; cout << ":) 请输入表达式：\n"; char str[MaxSize] = { 0 }; cin >> str; parse(str, &num_stack, &str_stack); } system("pause"); return 0; } //easy caculator // //Created by zzx on 2018