Hey friends! Please explain me this code and say why output is 478?

Question

#include <iostream>
using namespace std;
int x(int &a,int &b){
a =3;
b=4;
return a+b;
}

int main() {
int a=2;
int b=7;
int c=x(a,a);
cout<<a<<b<<c;
return 0;
}
//output :478

Answer 1

function x accepts two parameters a and b, both are passed by reference, meaning, assignment to either a and/or b will reflect actual value of a and/or b in the function caller scope.

(In main)
a = 2, b = 7

Calling x, passing 'a' as 1st & 2nd argument
(In func x)
a = 3 // here a = 3 (it was 2)
b = 4 // here a = 4 (it was 3)

NOTE: in main, we passed 'a' in place of parameter 'b', so here, again, a is assigned new value (4).

Return a + b (4 + 4) = 8
(Exit function x)

(Edit: Accidentally submitted)

(Back in main)
a = 4
b = 7 (no change)
c = 8 (returned from function x)
cout << a << b << c;
Output: 478

Hth, cmiiw