C++ if kullanmadan hesap makinesi yapma

#include <iostream>
 
using namespace std;
 
int main()
{
   int sayi1,sayi2,secim,sonuc;
   cout<<"Sayi giriniz :"; cin>>sayi1;
   cout<<"Sayi giriniz :"; cin>>sayi2;
   cout<<"Yapmak istediginiz islemi seciniz \n 1.Toplama \n 2.Cikarma \n 3.Carpma \n 4.Bolme \n"; cin>>secim;
 
   switch(secim)
   {
      case 1:
         sonuc=sayi1+sayi2;
         break;
      case 2:
         sonuc=sayi1-sayi2;
         break;
      case 3:
         sonuc=sayi1*sayi2;
         break;
      case 4:
         sonuc=sayi1/sayi2;
         break;
      default:
         cout<<"Lütfen 1 ile 4 arasında bir sayi giriniz";
         break;
   }
   cout<<"islem sonucunuz = "<<sonuc;
   return 0;
}

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

double sum(double num1, double num2) {
    return num1 + num2;
}
double sub(double num1, double num2) {
    return num1 - num2;
}
double multi(double num1, double num2) {
    return num1 * num2;
}
double divide(double num1, double num2) {
    return num1 / num2;
}

int main()
{
    map<string, function<double(double, double)>> operations;
    
    operations["+"] = sum;
    operations["-"] = sub;
    operations["*"] = multi;
    operations["/"] = divide;
    string op;
    double num1, num2, result=0.f;
    cin>>num1;
    cin>>num2;
    cin>>op;
    if (operations.find(op) != operations.end()) {
        result = operations[op](num1, num2);
    }
    cout << result << endl;
    return 0;
}

const operations = {
  "+": (n1, n2) => {
    return n1+n2;
  },
  "-": (n1, n2) => {
    return n1-n2;
  },
  "*": (n1, n2) => {
    return n1*n2;
  },
  "/": (n1, n2) => {
    return n1/n2;
  }
}

const num1 = 5, num2 = 10

const test = (expected, op) => {
  return expected === operations[op](num1, num2)
}

console.log(`
  sum test: ${test(num1 + num2, "+")},
  sub test: ${test(num1 - num2, "-")},
  mul test: ${test(num1 * num2, "*")},
  div test: ${test(num1 / num2, "/")},
`)