A certain company gives each of its clients a 10 digit number as a sort of identification code. As a precaution, any pair of used codes should differ by at least two digits so no one accidentally gives someone else's code.
How many clients can they have before adding digits? Give an example of a set of codes they might use. What if each pair of codes must differ by at least 3 digits? 4? More?
(In reply to
3+ digits? by Tristan)
In my earlier comment I wrote
"The set cannot be greater than this since if we change the last digit, then this number will only differ by one digit from some existing element e.g. abcdefgh01 differs by one from abcdefgh00 or abcdefgh11 which are in the full set."
If you read this in context, it does prove that no larger set exists?
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Posted by goFish
on 2006-02-25 18:04:31 |
re: 3+ digits?
