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XOR swap algorithm

MyRubyLearning

http://en.wikipedia.org/wiki/XOR_swap_algorithm

Conventional swapping requires the use of a temporary storage variable. Using the XOR swap algorithm, however, no temporary storage is needed. The algorithm is as follows:

X := X XOR Y
Y := X XOR Y
X := X XOR Y

To understand it, think about the PLUS swap algorithm
a = a + b
b = a – b
a = a -b

interpret XOR: it is a binary PLUS operation without carry.

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