Help 'reading' some code.

[nahla]

Here is some code, I was wondering if someone could explicitly describe what is going on throughout the code so I could better understand it. I have tried but I keep running into issues. Such as what do a and b refer to in the first, second, and third calls to swap(a,b)? Also I have a non-void error when trying to run this. Some clear explanation would help me solve further code.

#include <iostream>
#include <iomanip> // Required for setw() setprecision(), fixed.
#include <cmath>
using namespace std;


void swap(string& a, string& b)
{  string temp;
   temp = a;
   a = b;
   b = temp;
}

int three_card_monte(string card1, string card2, string card3)
{  swap(card1, card2);
   swap(card2, card3);
   swap(card1, card3);
   
   if (card1 == "queen")
      return 1;
   else if (card2 == "queen")
      return 2;
   else if  (card3 == "queen") 
      return 3;
}

int main()
{  string first = "queen";
   string second = "king";
   string third = "ace";
   int guess;
   int location;
         
   location = three_card_monte(first, second, third);
    
   cout << "Where's the Queen ( 1, 2 or 3 ) ? ";
   cin >> guess;

   if (guess == location)
      cout << "Congratulations!" << "\n";
   else
      cout << "Better luck next time, it was number " << location << "\n";
          
   return 0;
}

[Moschops]

Such as what do a and b refer to in the first, second, and third calls to swap(a,b)?

Always the same. a is the first parameter passed in, b is the second.