41 lines
812 B
Lua
41 lines
812 B
Lua
function checkIsbn13(isbn)
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local count = 0
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local sum = 0
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for c in isbn:gmatch"." do
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if c == ' ' or c == '-' then
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-- skip
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elseif c < '0' or '9' < c then
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return false
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else
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local digit = c - '0'
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if (count % 2) > 0 then
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sum = sum + 3 * digit
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else
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sum = sum + digit
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end
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count = count + 1
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end
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end
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if count ~= 13 then
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return false
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end
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return (sum % 10) == 0
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end
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function test(isbn)
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if checkIsbn13(isbn) then
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print(isbn .. ": good")
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else
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print(isbn .. ": bad")
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end
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end
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function main()
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test("978-0596528126")
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test("978-0596528120")
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test("978-1788399081")
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test("978-1788399083")
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end
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main()
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