Practice
ISBN to EAN
Design and code a function named EAN
that receives an International Standard Book Number (ISBN) and returns
the equivalent European Article Number (EAN). The ISBN
consists of up to 10 digits. The equivalent EAN consists of
13 digits where the leftmost 3 digits are 978 and the rightmost
digit is a check digit. The remaining 9 digits are the
same as the corresponding ISBN digits. For example,
ISBN: 321197186
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EAN: 9780321197184
The statement
printf("??\n", EAN( 321197186 ));
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where ?? is to be replaced by the appropriate conversion specifier, displays
The check digit for an EAN is the digit that adds to the weighted
sum of the other digits to produce a total that is divisible by 10.
The weighted sum is from the left:
- the sum of the 1st, 3rd, etc. digits (excluding the check digit), plus
- the sum of the 2nd, 4th, etc. digits each multiplied by 3.
That is,
EAN 978032119718?
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check digit is ?
9 7 8 0 3 2 1 1 9 7 1 8
x 1 3 1 3 1 3 1 3 1 3 1 3
= 9 21 8 0 3 6 1 3 9 21 1 24 = 106
remainder after division by 10 6 A
check digit is difference 10 - A 4
Therefore, the EAN is 9780321197184
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