perplexus.info :: Algorithms : Swap

Swap (Posted on 2004-01-02)

In programming, a common task is to swap the values of two variables. Lines 40-60 of the program below perform the swap using a temporary variable (T).

10 A=123
20 B=456
30 PRINT A,B
40 T=A
50 A=B
60 B=T
70 PRINT A,B

Rewrite the program to swap the values in A and B without using a temporary variable.

Note: The new program will not require sophisticated programming or complex math.

Submitted by Brian Smith

Rating: 3.2857 (7 votes)

Solution: (Hide)

The solution I originally intended was:

10 A=123
20 B=456
30 PRINT A,B
40 A=A+B
50 B=A-B
60 A=A-B
70 PRINT A,B

Others have suggested using XOR, since addition and subtraction can produce overflows

10 A=123
20 B=456
30 PRINT A,B
40 A=A XOR B
50 B=A XOR B
60 A=A XOR B
70 PRINT A,B

Comments: ( You must be logged in to post comments.)

Subject	Author	Date
Sophisticated programming or Math	brianjn	2004-01-08 01:26:40
re: solution	Federico Kereki	2004-01-05 11:07:48
Solution?	Stereo	2004-01-05 00:43:04
solution...	sunny	2004-01-04 18:29:43
No Math?	Richard	2004-01-02 21:51:47
re(2): other solutions	Richard	2004-01-02 21:47:58
re: other solutions	Tristan	2004-01-02 20:25:50
other solutions	Charlie	2004-01-02 17:03:48
re: solution	Gamer	2004-01-02 16:10:22
Nice!	stan	2004-01-02 16:04:54
solution	rerun141	2004-01-02 14:48:46

Please log in:

Login:
Password:
Remember me:

Sign up! \| Forgot password

Search:

Search body:

Forums (1)
Newest Problems
Random Problem
FAQ | About This Site
Site Statistics
New Comments (6)
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On

Chatterbox:


perplexus dot info