How come the open and close brackets not showing in the output? - c++

Question

In C++, I am trying to convert these infix expressions (, ), +, -, *, and / to postfix using stacks, but the output does not print out all of the inputs. Parenthesis is not showing in the output after the program runs. There are no errors too.
This image shows the output after it compiles:
The code:
#include <iostream>
#include <stack>
#include <strings.h>
using namespace std;
int operatorPrecedence(char operators);
void infixtoPostfix(string exp);
int main()
{
string exp;
cout << "Enter Infix Expression: "; cin >> exp;
infixtoPostfix(exp);
return 0;
}
int operatorPrecedence(char operators){
//Checking precedence of operators
if (operators == '/') return 2;
else if (operators == '*') return 2;
else if (operators == '+') return 1;
else if (operators == '-') return 1;
else return -1;
}
void infixtoPostfix(string exp){
stack<char> s;
s.push('N');//Element in stack to indicate end of stack
int len = exp.length();
string ns;//Final string for result
for(int i = 0; i < len; i++){
//Storing operand into display string
if ((exp[i] >= 'A' && exp[i] <= 'Z') || (exp[i] >= 'a' && exp[i] <='z') || (exp[i] >= '0' && exp[i] <= '9'))
ns += exp[i];
//Checking for braces/Parentheses
else if (exp[i] == '(')
s.push(exp[i]);
else if (exp[i] == ')'){
while (s.top() != 'N' && s.top() != '('){
char c = s.top();
s.pop();
ns += c;
}
//Popping parentheses if empty
if (s.top() == '('){
char c = s.top();
s.pop();
}
}
else{
//Checking whether scanned operator is less than operator stored in the stack
while (s.top() != 'N' && operatorPrecedence(exp[i]) <= operatorPrecedence(s.top())){
char c = s.top();
s.pop();
ns += c;
}
s.push(exp[i]);
}
}
//Popping out everything else stored in the stack
while (s.top() != 'N'){
char c = s.top();
s.pop();
ns += c;
}
cout << "Postfix Expression: " << ns << endl;
}