Example 1: Swapping integers.

swap1(a,b)     : call by value
swap2(a,b)     : call by reference.
swap2(a,b,c,d) : call by reference.

swap2 is overloaded.

#include <iostream>
using namespace std;

void swap1(int a, int b){
  int temp = a;
  a = b;
  b = temp;;

  return;
}

void swap2(int& a, int& b){
  int temp = a;
  a = b;
  b = temp;
  
  return;
}

void swap2(int& a, int& b, int& c, int& d) {
  swap2(a,b);
  swap2(c,d);
  
  return;
}

int main() {
  int num1, num2, num3, num4;

  cin >> num1 >> num2 >> num3 >> num4;
  swap1(num1, num2);
  cout << num1 << "  " << num2 << "\n";  // line A
  swap2(num1, num2);
  cout << num1 << "  " << num2 << "\n";  // line B
  
  swap2(num1,num2, num3,num4);
  cout << num3 << "  " << num4 << "\n";  // line C

  return 0;
}



Example 2 : Sorting integers.
This program sorts the integers in
decreasing order. This algorithm is
known as "selection sort".

#include<iostream>
using namespace std;

void swap(int& a, int& b) {
  int temp;

  temp = a;
  a = b;
  b = temp;

  return;
}

int find_max_index(int arr[], int low, int high) {
  int m, index, c;
  
  m=arr[low]; index=low;
  for(c=low + 1; c <= high; c++) {
    if (arr[c] > m) {
      m = arr[c];
      index = c;
    }
  }

  return index;
}
      

int main() {
  int a[10];
  int b,c;

  for(b=0;b<10;b++) {
    cin >> a[b];
  }

  for(b=0;b<9;b++){
    c = find_max_index(a,b,9);
    swap(a[b],a[c]);
  }
  
  for(b=0;b<10;b++)
    cout << a[b] << "  ";

  cout << endl;

  return 0;
}