My mathematical expression converter doesn't print correctly - c++

Question

So, I am writing a program which takes the input (a mathematical expression) and converts it into postfix notation and then print it out to the user. When I perform this program on simple mathematical expressions (i.e. 5 + 1 - 3 * 2) it works great. The problem is when I include parentheses. It prints all of the mathematical operators on the last line instead of their proper place. I need the mathematical operators to be in their proper spot. (i. e. 5 1 + 3 - 2 *). Any suggestions?
The real output of this statement 5 - ( 2 * 3 ) + 5 is 5 2 3 5 * - + I need it to look like 5 2 3 * - 5 +
#include <iostream>
#include <stack>
#include <string>
#include <sstream>
using namespace std;
int priority(string item) //prioritizing the operators
{
if(item == "(" || item == ")")
{
return 0;
}
else if(item == "+" || item == "-")
{
return 1;
}
else if(item == "/" || item == "*")
{
return 2;
}
}
void welcome()
{
cout << "blah blah!" << endl;
}
int main()
{
welcome(); // welcome text
stack <string> myStack;
char line[256];
cin.getline( line, 256);
string exp = line;
string item;
string output = "";
istringstream iss(exp);
iss >> item;
while(iss)
{
if(item != "+" && item != "-" && item != "/" && item != "*" && item != "(" && item != ")") //If the char is a number
{
cout << item << endl;
}
else if(myStack.size() == 0) // If the stack is empty
{
myStack.push(item);
}
else if( item == "+" || item == "-" || item == "/" || item == "*") //If the char is an operator
{
if(priority(myStack.top()) < priority(item)) // the item on the stack is greater priority than the array item
{
myStack.push(item);
}
else
{
while(myStack.size() > 0 && priority(myStack.top()) >= priority(item)) //while the stack contains something, and the item on
{
string dpu = myStack.top();
myStack.pop();
output = output + dpu + " ";
}
myStack.push(item);
}
}
else if(item == "(") // left peren
{
myStack.push(item);
}
else if(item == ")") // right peren
{
while(myStack.top() != "(")
{
string dpu = myStack.top();
myStack.pop();
output = output + dpu + " ";
}
myStack.pop();
}
iss>> item;
}
while (myStack.size() > 0 )
{
string dpu = myStack.top();
output = output + dpu + " ";
myStack.pop();
}
cout<< output << endl;
}

Answer 1

well... in your code the numbers are always printed before anything else:
if (item != "+" && item != "-" && item != "/" && item != "*" && item != "(" && item != ")") //If the char is a number
{
cout << item << endl;
}
I'm not familiar with the notation you are requesting, but a stack doesn't seem to me the right datastructure for this task... using a tree seems better to me, since you are parsing