Tiny Tricky Code

1. Swapping

The following piece of code is what I discovered by a glance to what my deskmate was reading:
It is about swapping and I think it can be applied to all kinds of data swapping if there is no high-level requirements involved. Until then, I was convinced that a temporary variable is inevitable in even the swapping of the simplest type. Although ccomplishing it without a temporary variable is probably the only merit of this code, it is very clever and inspiring.

The conventional way of swapping two entities:

  1. void swap(in out T a, in out T b)
  2. {
  3.     T t = b;
  4.     b = a;
  5.     a = t;
  6. }

The improved method:

  1. void swap(in out T a, in out T b)  // T supports ^ operation in the bitwise sense    
  2. {
  3.     a ^= b;
  4.     b ^= a;
  5.     a ^= b;
  6. }

Yes, it's that simple and easy to remember, just three XORs, despite its obscurity.




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