Infix to Postfix

bool is_operator(char x);

int main()
{

    string expression;
    cout<<"\tEnter Infix Expression: \n\t-->";
    getline(cin,expression);


    string postfix = Infix_Postfix(expression);

    cout<<"\n\tCorresponding Postfix Expression: \n\t-->"<<postfix;




    return 0;
}

bool is_operator(char x)
{
    if (x == '*' || x == '/' || x == '+' || x == '-')
      {
        return true;
      }
    else
      {
        return false;
      }
}


string Infix_Postfix(string X)
{
    STACK<char> s = STACK<char>();
    s.push('[');
    X.append("]");

    string Y;
    int index = 0;

    while(!s.is_empty())
    {
        for(int i = 0; i < X.length(); i++)
            {

                if(X[i] == '(')
                    {
                        s.push(X[i]);
                    }
                else if (X[i] == ')')
                        {
                            while(!s.is_empty() && s.get_top() != '(')
                                {
                                    Y = Y + s.get_top();
                                    s.pop();
                                }
                            s.pop();
                        }
                else if (is_operator(X[i]))
                    {
                        if(X[i] == '+' || X[i] == '-')
                            {
                                while(s.get_top() == '*' || s.get_top() == '/' || s.get_top() == '+' || s.get_top() == '-')
                                    {
                                        Y = Y + s.get_top();
                                        s.pop();
                                    }
                                s.push(X[i]);
                            }
                        else if (X[i] == '*' || X[i] == '/')
                            {
                                while(s.get_top() == '*' || s.get_top() == '/' )
                                    {
                                        Y = Y + s.get_top();
                                        s.pop();
                                    }
                                s.push(X[i]);
                            }

                    }
                else if (X[i] == ']')
                    {
                        while(s.get_top() != '[')
                            {
                                Y = Y + s.get_top();
                                s.pop();
                            }
                        s.pop();
                    }
                else
                    Y = Y + X[i];
            }
        return Y;
    }
}