스택 후위 표기식 기반 계산기

「과제」

스택을 사용하여 후위 표기식으로 변환하여 계산하는 계산기

조건1) 연산자 우선순위 무시하고 순서대로 계산한다

조건2) 괄호로 우선순위를 묶어 전달할 경우 그러한 우선순위를 지킨다

  입력: (3 * 5) - (6 / 2) 

  정답: 12

  입력 3 * 5 - 6 / 2

  정답: 4.5

「실행 화면」

「소스코드」

#include <iostream>
#include <iterator>
#include <vector>
using namespace std;
using namespace std::string_literals;
 
enum elementType
{
    OPERATEOR,
    OPERATION
};
 
struct element
{
    bool flag;
    char data_operator;
    double data_operation;
};
 
vector<element> Equation;
 
void ShowEquation(const vector<element> ShowString)
{
    for (element element_ : ShowString)
    {
        if (element_.flag == elementType::OPERATEOR)
        {
            cout << element_.data_operator << " ";
        }
        else
        {
            cout << element_.data_operation << " ";
        }
    }
    cout << endl;
}
 
void Convert_Postfix(const string* input)
{
    // refine
    double OperationNum = NULL;
    Equation.clear();
 
    for (int i = 0; i < input->size(); i++)
    {
        if (input->at(i) == '+' || input->at(i) == '-' || input->at(i) == '*' || input->at(i) == '/' || input->at(i) == '(' || input->at(i) == ')')
        {
            if (OperationNum != NULL)
            {
                Equation.push_back({ elementType::OPERATION, NULL, OperationNum });
                OperationNum = NULL;
            }
            Equation.push_back({ elementType::OPERATEOR, input->at(i), NULL });
        }
        else if (OperationNum == NULL)
        {
            OperationNum = input->at(i) - 48;
        }
        else
        {
            OperationNum *= 10;
            OperationNum += input->at(i) - 48;
        }
    }
 
    // Convert to postfix
    vector<element> Equation_ = Equation;
    vector<element> stack;
 
    Equation.clear();
 
    for (int i = 0; i < Equation_.size(); i++)
    {
        if (Equation_[i].flag == elementType::OPERATION)
        {
            Equation.push_back(Equation_[i]);
            continue;
        }
 
        switch (Equation_[i].data_operator)
        {
        case '(':
            stack.push_back({ elementType::OPERATEOR, '(', NULL });
            break;
        case ')':
            while (stack.back().data_operator != '(')
            {
                Equation.push_back(stack.back());
                stack.pop_back();
            }
            stack.pop_back();
            break;
        case '+':
        case '-':
        case '*':
        case '/':
            while (stack.size() != 0 && stack.back().data_operator != '(')
            {
                Equation.push_back(stack.back());
                stack.pop_back();
            }
            stack.push_back(Equation_[i]);
            break;
        }
    }
 
    size_t stackSize = stack.size();
    for (size_t i = 0; i < stackSize; ++i)
    {
        Equation.push_back(stack.back());
        stack.pop_back();
    }
}
 
double Calculate()
{
    vector<double> stack;
    double temp = 0;
 
    for (element data : Equation)
    {
        if (data.flag == elementType::OPERATION)
        {
            stack.push_back(data.data_operation);
            continue;
        }
 
        switch (data.data_operator)
        {
        case '+':
            temp = stack[stack.size() - 2] + stack.back();
            stack.pop_back(); stack.pop_back();
            stack.push_back(temp);
            break;
        case '-':
            temp = stack[stack.size() - 2] - stack.back();
            stack.pop_back(); stack.pop_back();
            stack.push_back(temp);
            break;
        case '*':
            temp = stack[stack.size() - 2] * stack.back();
            stack.pop_back(); stack.pop_back();
            stack.push_back(temp);
            break;
        case '/':
            temp = stack[stack.size() - 2] / stack.back();
            stack.pop_back(); stack.pop_back();
            stack.push_back(temp);
            break;
        }
    }
    return stack.front();
}
 
int main()
{
    string input;
 
    while (true)
    {
        cout << "Equation(exit = \"end\"): ";
        cin >> input;
 
        if (input == "end") 
        { 
            break; 
        }
 
        /* 계산코드 */
        input.insert(0, "(");
        input += ")";
        Convert_Postfix(&input);
        ShowEquation(Equation);
        cout << "answer: " << Calculate() << endl << endl;
    }
 
    system("pause");
    return 0;
}