Best way to exchange values of two integers?

Question

Possible Duplicate:
What is the fastest way to swap values in C?

I need to exchange values of two integers (for example x and y) This is the simplest way:

int temp = x;
x = y;
y = temp;

and I also found a better way:

x = x + y;
y = x - y;
x = x - y;

Is there a better way to increase performance?

There is **no possible way** that *either* of these pieces of code is a bottleneck in your application. — Cody Gray - on strike, Dec 20 '11 at 05:57
Unless you're asking this out of curiosity, you're wasting effort. Trust your compiler to produce efficient code for such a trivial operation. — Michael Petrotta, Dec 20 '11 at 05:58
possible duplicate of [What is the fastest way to swap values in C?](http://stackoverflow.com/questions/36906/what-is-the-fastest-way-to-swap-values-in-c), [Swap the values of two variables without using third variable](http://stackoverflow.com/questions/756750/swap-the-values-of-two-variables-without-using-third-variable), [Swap two variables without using a temp variable](http://stackoverflow.com/questions/804706/swap-two-variables-without-using-a-temp-variable), *etc. etc. etc.* — Cody Gray - on strike, Dec 20 '11 at 06:02

score 4 · Accepted Answer · answered Dec 20 '11 at 06:03

4

it is posible with XOR "^" operator:

  a = a^b;
  b = a^b;
  a = a^b;

answered Dec 20 '11 at 06:03

Artur Keyan

yes, XOR is faster than + operator.Thank you. – shift66 Dec 20 '11 at 06:06
5

@Ademiban: Quote from wiki "Most modern compilers can optimize away the temporary variable in the naive swap, in which case the naive swap uses the same amount of memory and the same number of registers as the XOR swap and is at least as fast, and often faster." – Jesse Good Dec 20 '11 at 06:11
I dont know )) I have x=5 y=3 after that x is 0, y is 5.in Java – shift66 Dec 20 '11 at 06:19
@Ademiban No way! check again with different values. :)) – COD3BOY Dec 20 '11 at 06:26
:D it's wrong way if it works wrong for at least one case. – shift66 Dec 20 '11 at 06:28

score 2 · Answer 2 · answered Dec 20 '11 at 05:59

2

Well in the second option you use 2 variables instead of 3 in the 1st option, this means you allocate less memory.

answered Dec 20 '11 at 05:59

CloudyMarble

yes and I wanna know is there a better way? say, do it with two operators. – shift66 Dec 20 '11 at 06:01

2 Answers2