uses reference parameters to swap the values of the variables it is called with : pointer reference « Pointer « C++ Tutorial

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2. Pointer
3. pointer reference

#include <iostream>
using namespace std;
   
void swap(int &i, int &j);
   
int main()
{
  int a, b, c, d;
   
  a = 1;
  b = 2;
  c = 3;
  d = 4;
   
  cout << "a and b: " << a << " " << b << "\n";
  swap(a, b); // no & operator needed
  cout << "a and b: " << a << " " << b << "\n";
   
  cout << "c and d: " << c << " " << d << "\n";
  swap(c, d);
  cout << "c and d: " << c << " " << d << "\n";
   
  return 0;
}
   
void swap(int &i, int &j)
{
  int t;
   
  t = i; // no * operator needed
  i = j;
  j = t;
}