An easy way to swap 2 variables without using another variable:

C++ Syntax (Toggle Plain Text)

a=a+b;
b=a-b;
a=a-b;

a=a+b; b=a-b; a=a-b;

>The most efficient way for swapping whole numbers is <snip xor swap>
>because xor is an assembly level instruction and its much faster than any move operation.
An empirical test disproves your claim. The swap using a temporary is noticeably faster on at least one compiler (Microsoft C++) given any optimization level.

C++ Syntax (Toggle Plain Text)

#include <climits>
#include <ctime>
#include <iostream>
 
void swap_temp ( int& a, int& b )
{
  int temp = a;
  a = b;
  b = temp;
}
 
void swap_xor ( int& a, int& b )
{
  a ^= b;
  b ^= a;
  a ^= b;
}
 
int main()
{
  int a1 = 10, a2 = 20;
  int b1 = 10, b2 = 20;
  std::clock_t start;
 
  std::cout<< a1 <<"\t"<< a2 <<'\n';
  std::cout<< b1 <<"\t"<< b2 <<'\n';
 
  swap_temp ( a1, a2 );
  swap_temp ( b1, b2 );
 
  std::cout<< a1 <<"\t"<< a2 <<'\n';
  std::cout<< b1 <<"\t"<< b2 <<'\n';
 
  std::cout<<"swap_temp: ";
  start = std::clock();
  for ( unsigned i = 0; i < UINT_MAX; i++ )
    swap_temp ( a1, a2 );
  std::cout<< static_cast<double> ( std::clock() ) - start / CLOCKS_PER_SEC <<'\n';
 
  std::cout<<"swap_xor: ";
  start = std::clock();
  for ( unsigned i = 0; i < UINT_MAX; i++ )
    swap_temp ( b1, b2 );
  std::cout<< static_cast<double> ( std::clock() ) - start / CLOCKS_PER_SEC <<'\n';
}

#include <climits> #include <ctime> #include <iostream> void swap_temp ( int& a, int& b ) { int temp = a; a = b; b = temp; } void swap_xor ( int& a, int& b ) { a ^= b; b ^= a; a ^= b; } int main() { int a1 = 10, a2 = 20; int b1 = 10, b2 = 20; std::clock_t start; std::cout<< a1 <<"\t"<< a2 <<'\n'; std::cout<< b1 <<"\t"<< b2 <<'\n'; swap_temp ( a1, a2 ); swap_temp ( b1, b2 ); std::cout<< a1 <<"\t"<< a2 <<'\n'; std::cout<< b1 <<"\t"<< b2 <<'\n'; std::cout<<"swap_temp: "; start = std::clock(); for ( unsigned i = 0; i < UINT_MAX; i++ ) swap_temp ( a1, a2 ); std::cout<< static_cast<double> ( std::clock() ) - start / CLOCKS_PER_SEC <<'\n'; std::cout<<"swap_xor: "; start = std::clock(); for ( unsigned i = 0; i < UINT_MAX; i++ ) swap_temp ( b1, b2 ); std::cout<< static_cast<double> ( std::clock() ) - start / CLOCKS_PER_SEC <<'\n'; }