Thursday Code Puzzler: ISBN Validator
Thursday Code Puzzler: ISBN Validator
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Check if a given string is an ISBN number
Write a method that will take a string parameter and check if it conforms to the ISBN-13 specification as detailed in Wikipedia.
The calculation of an ISBN-13 check digit begins with the first 12 digits of the thirteen-digit ISBN (thus excluding the check digit itself). Each digit, from left to right, is alternately multiplied by 1 or 3, then those products are summed modulo10 to give a value ranging from 0 to 9. Subtracted from 10, that leaves a result from 1 to 10. A zero (0) replaces a ten (10), so, in all cases, a single check digit results.
Formally, the ISBN-13 check digit calculation is:
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