Let's say I have variable holding 3 and another holding 5. I need to switch their values without another variable. How can I do it?
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4Why would you need to do that without using a separate variable? I can't see any reason for that other than for writing convoluted code. It's definitely not a real-world problem. – Jon Skeet Oct 05 '13 at 19:42
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How **not** to do? Asks Yoda. By the way, Google, or even the search finction in the good old common Wikipeadia would have yielded you a nice and thorough answer... – ppeterka Oct 05 '13 at 19:42
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1XOR swap idiom for low-memory chips. But a mature compiler would optimize it. – huseyin tugrul buyukisik Oct 05 '13 at 19:45
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Sounds like an interview question. Of course you would never do this in real code. – Peter Lawrey Oct 05 '13 at 19:48
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I saw that somewhere, promptly forgot it as complete useless.... – Tony Hopkinson Oct 05 '13 at 19:49
1 Answers
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It can be done using bitwise XOR:
x ^= y;
y ^= x;
x ^= y;
This is known as the XOR swap algorithm (that Wikipedia article goes into detail about how this works, so I suggest you read it).
However, this isn't particularly understandable (not to mention it only works on integral types), so in nearly all contexts using a temporary variable would be preferred:
int tmp = x;
x = y;
y = tmp;
arshajii
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