giles
07de86365e
Some checks failed
Test, Build, and Deploy / test-build-deploy (push) Failing after 27s
Walks digits right-to-left, doubles every other starting from the
second-from-right; if a doubled value > 9, subtract 9. Sum must be
divisible by 10:
let luhn s =
let n = String.length s in
let total = ref 0 in
for i = 0 to n - 1 do
let d = Char.code s.[n - 1 - i] - Char.code '0' in
let v = if i mod 2 = 1 then
let dd = d * 2 in
if dd > 9 then dd - 9 else dd
else d
in
total := !total + v
done;
!total mod 10 = 0
Test cases:
'79927398713' valid
'79927398710' invalid
'4532015112830366' valid (real Visa test)
'1234567890123456' invalid
sum = 2
Tests right-to-left index walk via 'n - 1 - i', Char.code '0'
arithmetic for digit conversion, and nested if-then-else.
75 baseline programs total.
21 lines
479 B
OCaml
21 lines
479 B
OCaml
let luhn s =
|
|
let n = String.length s in
|
|
let total = ref 0 in
|
|
for i = 0 to n - 1 do
|
|
let d = Char.code s.[n - 1 - i] - Char.code '0' in
|
|
let v = if i mod 2 = 1 then
|
|
let dd = d * 2 in
|
|
if dd > 9 then dd - 9 else dd
|
|
else d
|
|
in
|
|
total := !total + v
|
|
done;
|
|
!total mod 10 = 0
|
|
|
|
;;
|
|
|
|
(if luhn "79927398713" then 1 else 0)
|
|
+ (if luhn "79927398710" then 1 else 0)
|
|
+ (if luhn "4532015112830366" then 1 else 0)
|
|
+ (if luhn "1234567890123456" then 1 else 0)
|