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# swap without using temp variable

Seetharaman Venkatasamy
Ranch Hand
Posts: 5575
how to swap the values without using temp variable

please can you tell me ?

Thanks & Regards,
seetharaman.v
[ May 28, 2008: Message edited by: David O'Meara ]

David O'Meara
Rancher
Posts: 13459
http://prabhagovind.wordpress.com/2007/02/09/3-ways-to-swap-variables-without-temp-variable/

Personally I'd just use a temp variable...

Seetharaman Venkatasamy
Ranch Hand
Posts: 5575
Thanks David ...i got the tricky

amitabh mehra
Ranch Hand
Posts: 98
you can do it in a single step:

sandeep thatikonda
Greenhorn
Posts: 1
you can swap as shown below without using temp

let a and b are two variables to swap for example let a=5 b= 3

step 1)a=a+b ------------ > a=5+3=8

step 2)b=a-b ------------ > b=8-3=5

step 3)a=a-b ------------ > a=8-5=3

finally a=3 ,b=5 hence swaped

Karthikeyan Ramaswamy
Ranch Hand
Posts: 42
hi,

you can swap like that also,

let a=5 b= 3

a=a*b ------------ > a=5*3=15

b=a/b ------------ > b=15/3=5

a=a/b ------------ > a=15/5=3

result a=3,b=5

-----------------------

Campbell Ritchie
Sheriff
Posts: 50702
83
Welcome to JavaRanch, Sandy

I like Karthikeyan Ramaswamy's method! There is supposed to be a way to do it with the bitwise XOR operator ^ but I can't remember how to do it.

Karthikeyan Ramaswamy
Ranch Hand
Posts: 42
hi, Campbell

Using bitwise XOR operator

int a=10,b=20;

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

result a=20,b=10

-----------------

Campbell Ritchie
Sheriff
Posts: 50702
83
Thank you.

Jesper de Jong
Java Cowboy
Saloon Keeper
Posts: 15568
46
If you're writing a serious piece of software, please do not use tricks like the above to swap the values of variables. They are clever tricks, but nothing more than that. You gain nothing by using these tricks in any piece of software - it's not faster and doesn't use more memory than just using a temp variable.

Note that the above methods by adding / subtracting or multiplying / dividing don't work for all values. Integers can overflow, and dividing by zero leads to errors as well.

Peter Chase
Ranch Hand
Posts: 1970
Yes, this stuff is all sorta kinda fun, but pointless.

Perhaps it was an interview question? If so, it doesn't say much for the interviewer. There are a small set of tricks like this, which people can easily learn for interviews, without actually knowing much about programming at all. Whereas many good honest candidates wouldn't know the answer, because they've been too busy working on real projects!

Interviewers should ask searching questions with longer answers, where it's much harder to fake a good answer. Of course, if the interviewer's own technical knowledge is lacking, and they're only looking for the "right" answer they've got on their crib-sheet, there's trouble there, too.

Rob Spoor
Sheriff
Posts: 20709
68
"sandy th",