No of registers

Question

What is minimum number of extra registers are required to swap 2 numbers, where 2 numbers are stored in two different registers?

Comments

0 extra registers.

R1 = R1+R2

R2 = R1-R2

R1 = R1 -R2

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say both registers contains value 8
then will it be swapped?

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Yes

R1 = 8, R2 = 8

R1 = 8+8 = 16

R2 = 16-8 = 8

R1 = 16-8 = 8

swapped. Result will be same. But what we want to achieved is achieved.