From 38610bdd115b65904a129dad6ba0533eb8332fd1 Mon Sep 17 00:00:00 2001
From: Jethro Stapelbroek <js@jethrostapelbroek.nl>
Date: Tue, 17 Oct 2023 22:46:33 +0200
Subject: [PATCH] Luhn's Checksum Algorithm

---
 luhnchecksum.py | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)
 create mode 100644 luhnchecksum.py

diff --git a/luhnchecksum.py b/luhnchecksum.py
new file mode 100644
index 0000000..fb6bff5
--- /dev/null
+++ b/luhnchecksum.py
@@ -0,0 +1,21 @@
+def luhn_checksum(card_number):
+    def digits_of(n):
+        return [int(d) for d in str(n)]
+
+    digits = digits_of(card_number)
+    odd_digits = digits[-1::-2]
+    even_digits = digits[-2::-2]
+    checksum = 0
+    checksum += sum(odd_digits)
+    for d in even_digits:
+        checksum += sum(digits_of(d * 2))
+    return checksum % 10
+
+
+def is_luhn_valid(card_number):
+    return luhn_checksum(card_number) == 0
+
+
+n = int(input())
+for _ in range(n):
+    print("PASS" if is_luhn_valid(input()) else "FAIL")