[数据结构]Stack_Calculator（中序波兰式转后序波兰式）

//Stack_Calculator.h
#pragma once
const int maxlength = 100;
class Calculator
{
public:
Calculator();
void transform();
void calc();

private:
int number_count;
char Reverse_Polish[maxlength];
};

//Stack_Calculator.cpp
#include "Stack_Calculator.h"
#include<string>
#include<iostream>
#include<stack>
#include<math.h>
using namespace std;
Calculator::Calculator()
{
number_count = 0;
}

void Calculator::transform()
{
stack<char>operate;
cout << "please enter a expression you want to calculate." << endl;
string enter;
cin >> enter;
for (unsigned int i = 0; i < enter.length(); i++)
{
if (enter[i] >= '0'&&enter[i] <= '9'||enter[i]=='-'&&i==0||enter[i]=='-'&&(enter[i-1]<'0'||enter[i-1]>'9')) {
//读取数字（包括负数），负数要注意不能与减号混淆
Reverse_Polish[number_count++] = '#';
Reverse_Polish[number_count++] = enter[i];
i++;
while (i < enter.length() && enter[i] >= '0'&&enter[i] <= '9' || enter[i] == '.') {
Reverse_Polish[number_count++] = enter[i];
i++;
}
i--;
continue;
}
switch (enter[i])
{
case '+':
case '-':
{
if (operate.empty() || operate.top() != '*'&&operate.top() != '/')
//判断栈内操作符优先级是否比当前操作符大，不大于，入栈
operate.push(enter[i]);
else if (operate.top() == '*' || operate.top() == '/') {
//大于，当前括号域中所有符号依次pop入后续表达式数组
while (!operate.empty() && operate.top() != '(') {
Reverse_Polish[number_count++] = operate.top();
operate.pop();
}
//pop出后push入栈
operate.push(enter[i]);
}
break;
}
case '*':
case'/':
case'(':
operate.push(enter[i]);
break;
case ')':
//右括号出现时，将与之匹配的左括号之间的所有操作数依次pop入后续表达式
{
while (operate.top() != '(') {
Reverse_Polish[number_count++] = operate.top();
operate.pop();
}
operate.pop();//pop掉左括号
break;
}
}
}
while (!operate.empty()) {
//将剩余操作符依次pop到后续表达式
Reverse_Polish[number_count++] = operate.top();
operate.pop();
}
/*for (int i = 0; i < number_count; i++)
cout << Reverse_Polish[i] << ' ';
cout << endl;*/
}

void Calculator::calc()
{
stack<double>calc;
for (int i = 0; i < number_count;) {
double current;
double a, b;
bool point = 0;
bool negative = 0;
int num = 0;
switch (Reverse_Polish[i])
{
case '#':
current = 0;
i++;
if (Reverse_Polish[i] == '-') {
negative = 1;
i++;
}
while (i < number_count && Reverse_Polish[i] >= '0'&&Reverse_Polish[i] <= '9'||
i < number_count &&Reverse_Polish[i]=='.') {
if (Reverse_Polish[i] == '.') {
point = 1;
i++;
continue;
}
current = current * 10 + Reverse_Polish[i++] - '0';
if (point)num++;
}
if(negative) calc.push(-current / pow(10, num));
else calc.push(current/pow(10,num));
/*cout << calc.top() << endl;*/
break;
case '+':
if (calc.empty()) {
number_count = 0;
cout << "invalidate enter please enter again(error:pop first error)" << endl;
transform();
Calculator::calc();
return;
}
a=calc.top();
calc.pop();
if (calc.empty()) {
cout << "invalidate enter please enter again(error:pop second error)" << endl;
number_count = 0;
transform();
Calculator::calc();
return;
}
b=calc.top();
calc.pop();
calc.push(a + b);
i++;
break;
case '-':
if (calc.empty()) {
number_count = 0;
cout << "invalidate enter please enter again(error:pop first error)" << endl;
transform();
Calculator::calc();
return;
}
a = calc.top();
calc.pop();
if (calc.empty()) {
number_count = 0;
cout << "invalidate enter please enter again(error:pop second error)" << endl;
transform();
Calculator::calc();
return;
}
b = calc.top();
calc.pop();
calc.push(b - a);
i++;
break;
case '*':
if (calc.empty()) {
number_count = 0;
cout << "invalidate enter please enter again(error:pop first error)" << endl;
transform();
Calculator::calc();
return;
}
a = calc.top();
calc.pop();
if (calc.empty()) {
number_count = 0;
cout << "invalidate enter please enter again(error:pop second error)" << endl;
transform();
Calculator::calc();
return;
}
b = calc.top();
calc.pop();
calc.push(a * b);
i++;
break;
case '/':
if (calc.empty()) {
number_count = 0;
cout << "invalidate enter please enter again(error:pop first error)" << endl;
transform();
Calculator::calc();
return;
}
a = calc.top();
calc.pop();
if (calc.empty()) {
number_count = 0;
cout << "invalidate enter please enter again(error:pop second error)" << endl;
transform();
Calculator::calc();
return;
}
b = calc.top();
calc.pop();
calc.push(b / a);
i++;
break;
default:
cout << "invalidate enter please enter again(error:calculate error)" << endl;
number_count = 0;
transform();
Calculator::calc();
return;
}
}
if (calc.empty()) {
cout << "invalidate enter please enter again(error:pop result error)" << endl;
transform();
Calculator::calc();
return;
}
else 	cout << calc.top() << endl;
}

//main.cpp
#include<iostream>
#include<string>
#include<stack>
#include"Stack_Calculator.h"
using namespace std;
void main() {
while (1) {
Calculator test;
test.transform();
test.calc();
}
}