as2.cpp

#include <iostream>
#include <string>
using namespace std;

#define SIZE 100
#define EOS '\0'

class op_stack {
    char s[SIZE];
    int top;
public : 
    op_stack();
    void push(char x);
    char pop();
    bool empty();
    char top_element();
};
    
op_stack::op_stack() 
{
    top = 0;
}

void op_stack::push(char x)
{
    s[top] = x;
    top++;
}

char op_stack::pop()
{
    top--;
    return(s[top]);
}

bool op_stack::empty()
{
    return (top == 0);
}

char op_stack::top_element()
{
    return(s[top-1]);
}

bool is_operand(char ch)
{
    if((ch == '(')||(ch == ')')||(ch == '+')||(ch == '-')||(ch == '*')||(ch == '/')||(ch == '%')||(ch == '$'))
        return false;
    else    return true;
}

int get_precedence(char op)
{
    if((op == EOS)||(op == '('))
        return (0);
    if((op == '+')||(op == '-'))
        return (1);
    if((op == '*')||(op == '/')||(op == '%'))
        return(2);
    return(-1);
}

int main()
{
    string input, output, prece, top;
    op_stack stack1;

    cout << "Input an infix expretion to convert : ";
    cin >> input;
    input += EOS;

    stack1.push(EOS);
    for(int i = 0 ; i < input.size() ; i++) // 인풋으로 받은 거 하나씩 인식
    {
        int toppre = get_precedence(stack1.top_element());
        if(is_operand(input[i])){ // 연산자가 아니면 아웃풋에 추가
            output += input[i];
            cout << output[i] << endl;
        }
        else
        {
            if(input[i] == '(') // ( 라면
                stack1.push(input[i]);
            else if(input[i] == ')')
            {
                while (stack1.top_element() != '(')
                    output += stack1.pop();
                stack1.pop();
            }
            else
            {
                while(get_precedence(input[i]) <= get_precedence(stack1.top_element()))
                    output += stack1.pop();
                stack1.push(input[i]);
            }

        }
    }

    while(!stack1.empty() && stack1.top_element() != EOS)
        output += stack1.pop();

    cout << output;
}