ISBN-10-Validation

Description

ISBN-10 identifiers are ten digits long. The first nine characters are digits 0-9. The last digit can be 0-9 or X, to indicate a value of 10.

An ISBN-10 number is valid if the sum of the digits multiplied by their position modulo 11 equals zero.

For example:

ISBN     : 1 1 1 2 2 2 3 3 3  9
position : 1 2 3 4 5 6 7 8 9 10

This is a valid ISBN, because:

(1*1 + 1*2 + 1*3 + 2*4 + 2*5 + 2*6 + 3*7 + 3*8 + 3*9 + 9*10) % 11 = 0

Examples

1112223339   -->  true
111222333    -->  false
1112223339X  -->  false
1234554321   -->  true
1234512345   -->  false
048665088X   -->  true
X123456788   -->  false

Solutions

Julia

# ISBN-10-Validation.jl


"""
解析每一位数字，'X'解析为10
"""

#> "解析每一位数字，'X'解析为10\n"

function parse_isbn(isbn::String)::Vector{Int8}
    isbn |> collect .|> x -> isdigit(x) ? parse(Int8, x) : 10
end

#> parse_isbn (generic function with 1 method)

function isvalidISBN10(isbn::String)::Bool
    form_check = occursin(r"^\d{9}(\d|X)$", isbn)
    !form_check && return false

    arithmetic_check = sum(parse_isbn(isbn) .* (1:10)) % 11 == 0
    return arithmetic_check
end

#> isvalidISBN10 (generic function with 1 method)

isvalidISBN10("1293")

#> false

isvalidISBN10("1112223339")

#> true

isvalidISBN10("1234512345")

#> false

isvalidISBN10("X123456788")

#> false