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Swap (Posted on 2004-01-02) Difficulty: 2 of 5
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.

See The Solution Submitted by Brian Smith    
Rating: 3.2857 (7 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
re: solution | Comment 10 of 11 |
(In reply to solution by rerun141)

That code might cause an overflow/underflow problem. (A+B could be too high/low.) If you have binary logic, you can rather write


A=A XOR B
B=A XOR B
A=A XOR B

which doesn't cause any problems.
  Posted by Federico Kereki on 2004-01-05 11:07:48
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