问题
I was told that using a temp object was not the most effective way to swap elements in an array.
Such as:
Object[] objects = new Object[10];
// -- Assign the 10 objects some values
var Temp = objects[2];
objects[2] = objects[4];
objects[4] = Temp;
Is it really possible to swap the elements of the array without using another object?
I know that with math units you can but I cannot figure out how this would be done with any other object type.
回答1:
Swapping objects with a temporary is the most correct way of doing it. That should rank way higher up in your priorities than speed. It's pretty easy to write fast software that ouputs garbage.
When dealing with objects, you just cannot do it differently. And this is not at all inefficient. An extra reference variable that points to an already existing object is hardly going to be a problem.
But even with numerical values, most clever techniques fail to produce correct results at some point.
回答2:
It's possible the person who told you this was thinking of something like this:
objects[2] = Interlocked.Exchange(ref objects[4], objects[2]);
Of course, just because this is one line doesn't mean it isn't also using a temporary variable. It's just hidden in the form of a method parameter (the reference to objects[2] is copied and passed to the Exchange method), making it less obvious.
回答3:
you could do it with Interlocked.Exchange but that won't be faster than using a temp variable... not that speed is likely to matter for this sort problem outside of an interview.
回答4:
Every example I can find online uses exactly this method to swap 2 elements in an array. In fact, if this were something I were doing often I would definately consider a generic extansion method, akin to this example:
http://w3mentor.com/learn/asp-dot-net-c-sharp/c-collections-and-generics/generically-swapping-two-elements-in-array-using-ccsharp/
回答5:
The only time you should worry about creating a temporary object is when its massive, and the time taken to copy the object will be sufficiently long and if you're doing it a lot, for example, or if youre doing a sort of 10k items, and moving it from 9999 to 1, 1 stage at a time testing if it should move or not, then swapping it each and every time would be a drain. However, a more efficient way would test all the tests and move once.
来源：https://stackoverflow.com/questions/6068856/c-sharp-swapping-objects-without-a-placeholder