Infix to postix.cpp

#include<string>
#include<iostream>
#include<stack>
#include<ctype.h>
using namespace std;

int GetOperatorWeight(char op)
{     /*Assign Weights to operators*/
  int weight = -1;
  switch(op)
  {
  case '+':
  case '-':
    weight = 1;
    break;
  case '*':
  case '/':
    weight = 2;
    break;
  case '^':
    weight = 3;
    break;
  }
  return weight;
}

int higherprecedence(char op1 , char op2)
{     /*Compares two operands, returns on with larger weight*/
  int op1Weight = GetOperatorWeight(op1);
  int op2Weight = GetOperatorWeight(op2);
  return (op1Weight>= op2Weight ?  1:0);
}

string itp(string exp)
{     /*function that converts infix to postfix*/
  int i;
  stack<char> S;
  string res;
  res.clear();
  for(i=0;i<exp.length();i++)
  {                        //Iterates over characters
    char ch=exp[i];
    if(ch=='('){
      S.push(ch);
    }
    else if(ch==')')
    {
      while(!S.empty() && S.top()!='(')
      {                  //Pop and add to result till '(' encountered, or stack empty
        res += ' ';
        res+=S.top();
        S.pop();
      }
      S.pop();          //Pop to remove '('
    }
    else if(GetOperatorWeight(ch) == -1){   //Add to result if not a supported operand
      res += ch;
    }
    else if(S.empty() || higherprecedence(S.top(),ch)==0){
      S.push(ch);       //Push on empty stack or if ch precedes top element
      res += ' ';
    }
    else if(higherprecedence(S.top(),ch)==1)
    {                   //Pop till '(' or lower precedence operand encountered, or stack empty
      while(!S.empty() && higherprecedence(S.top(),ch)==1 && S.top()!='('){
        res += ' ';
        res+=S.top();
        S.pop();
      }
      S.push(ch);       //Push new operand
      res += ' ';
    }
  
  }
  while(!S.empty())
  {         //To empty stack after expression iteration completed
    res += ' ';
    res+=S.top();
    S.pop();
  }
  return res;
}
int main(){
  cout << "This program converts infix expression to postfix expression\n";
  string exp;
  cout << "Enter an infix expression :";
  cin >> exp;
  string postfix = itp(exp);
  cout << "Output = " << postfix << "\n";
}