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The Standard Template Library overloads its built-in swap function to exchange the contents of containers efficiently this way. [1] As pointer variables are usually of a fixed size (e.g., most desktop computers have pointers 64 bits long), and they are numeric, they can be swapped quickly using XOR swap.
Using the XOR swap algorithm to exchange nibbles between variables without the use of temporary storage. In computer programming, the exclusive or swap (sometimes shortened to XOR swap) is an algorithm that uses the exclusive or bitwise operation to swap the values of two variables without using the temporary variable which is normally required.
In the C++ Standard Library, several algorithms use unqualified calls to swap from within the std namespace. As a result, the generic std::swap function is used if nothing else is found, but if these algorithms are used with a third-party class, Foo, found in another namespace that also contains swap(Foo&, Foo&), that overload of swap will be used.
Many C compilers support using compare-and-swap either with the C11 <stdatomic.h> functions, [8] or some non-standard C extension of that particular C compiler, [9] or by calling a function written directly in assembly language using the compare-and-swap instruction.
Selection sort can be implemented as a stable sort if, rather than swapping in step 2, the minimum value is inserted into the first position and the intervening values shifted up. However, this modification either requires a data structure that supports efficient insertions or deletions, such as a linked list, or it leads to performing Θ ( n 2 ...
The function swap() in the preceding example can be made thread-safe by making tmp thread-local. It still fails to be reentrant, and this will continue to cause problems if isr() is called in the same context as a thread already executing swap() :
2-opt. In optimization, 2-opt is a simple local search algorithm for solving the traveling salesman problem.The 2-opt algorithm was first proposed by Croes in 1958, [1] although the basic move had already been suggested by Flood. [2]
The getcontext function does not provide a return value to distinguish the cases (its return value is used solely to signal error), so the programmer must use an explicit flag variable, which must not be a register variable and must be declared volatile to avoid constant propagation or other compiler optimizations.