How to swap two variables in one line in C?

Question

I want to know that is there any other way of swapping 2 numbers in one line and of course without 3rd variable.

I know one way of doing this:

b=a+b-(a=b)

or

a=a+b-(b=a)

both are same(approximately). If you know then please help me out.

Why do you want to do this? Making code unreadable just to avoid using a 3rd variable — Ed Heal, Aug 23 '13 at 04:19
`a/=b=(a=a*b)/b;` Multiplication and division instead of addition and subtraction? — Abijeet Patro, Aug 23 '13 at 04:19
Both of your example methods invoke undefined behavior in C, as you are modifying a variable and using its value in the same expression. — verbose, Aug 23 '13 at 04:19
It may be possible in some cases but anyone that thinks it's a good idea is a fool. — Blastfurnace, Aug 23 '13 at 04:33

score 12 · Answer 1 · answered Aug 23 '13 at 04:23

12

The frequently cited classic answer that you are probably looking for is:

a^=b^=a^=b;

But, it is technically wrong, because it changes the same variable more than once before a sequence point.

answered Aug 23 '13 at 04:23

abelenky

score -1 · Answer 2 · answered Aug 23 '13 at 04:21

-1

Use bit twiddling in C. Following swap two variables:

if (a != b) { 
   a ^= b ^= a ^= b;
}

answered Aug 23 '13 at 04:21

Manoj Awasthi

5

This is undefined behavior since the same variable is modified twice. – Vaughn Cato Aug 23 '13 at 04:22

2 Answers2