The method of variable value Exchange: The third of eclectic programming

The topic is known as two variables A and B, and an algorithm is designed to exchange the values of A and B.

"Method 1" is the most traditional, broadest and most famous method of adding a variable to the code as follows:

int a, b;
int c;
c=a;
a=b;
b=c;

"Method 2" does not add a third variable, swapping the values of A and B, the code is as follows:

int a, b;
a = a+b;
b = a-b;
a=a-b;

Analysis, set A and b the original value of A,b

执行代码　　　变量a　　　　　 　变量b

int a, b　　　a　　　　　　　　　b

a=a+b　　　　 a+b　　　　　　　　 b

b=a-b　　　　a+b　　　　　　　 a+b-b=a

a=a-b　　　　a+b-(b)=a+b-a=b　　　a

"But" this method is only suitable for the integer type and so on, and can not be too large, otherwise there will be overflow.

"Method 3" bitwise operation

执行代码　　变量a　　　　　变量b

a=a^b;　　　a^b　　　　　　b
b=a^b;　　　a^b　　　　　　a^b^b=a
a=a^b;　　　a^b^a=b　　　　a
(异或)

"Ask" we usually use Method 1, Method 2 and Method 3 use less, also know that the following two is less than the 1th way to use a space, but the next two methods used in where?

"Answer": I have not met the use of the place. This is purely a research study that provides a variety of solutions.