1 files changed, 74 insertions, 0 deletions
diff --git a/challenge-308/pokgopun/python/ch-2.py b/challenge-308/pokgopun/python/ch-2.py
new file mode 100644
index 0000000000..5be727177d
--- /dev/null
+++ b/challenge-308/pokgopun/python/ch-2.py
@@ -0,0 +1,74 @@
+### https://theweeklychallenge.org/blog/perl-weekly-challenge-308/
+"""
+
+Task 2: Decode XOR
+
+Submitted by: [47]Mohammad Sajid Anwar
+     __________________________________________________________________
+
+   You are given an encoded array and an initial integer.
+
+   Write a script to find the original array that produced the given
+   encoded array. It was encoded such that encoded[i] = orig[i] XOR orig[i
+   + 1].
+
+Example 1
+
+Input: @encoded = (1, 2, 3), $initial = 1
+Output: (1, 0, 2, 1)
+
+Encoded array created like below, if the original array was (1, 0, 2, 1)
+$encoded[0] = (1 xor 0) = 1
+$encoded[1] = (0 xor 2) = 2
+$encoded[2] = (2 xor 1) = 3
+
+Example 2
+
+Input: @encoded = (6, 2, 7, 3), $initial = 4
+Output: (4, 2, 0, 7, 4)
+     __________________________________________________________________
+
+   Last date to submit the solution 23:59 (UK Time) Sunday 16^th February
+   2025.
+     __________________________________________________________________
+
+SO WHAT DO YOU THINK ?
+"""
+### solution by pokgopun@gmail.com
+
+def decodeXOR(enc: tuple[int], init: int) -> tuple[int]:
+    org = [init]
+    for i in range(len(enc)):
+        o = 0
+        if enc[i] == org[i]: ### a ^ o = a --> o = 0
+            pass
+        elif enc[i] == 0: ### a ^ o = 0 --> o = a
+            o = org[i]
+        elif org[i] == 0: ### 0 ^ o = a --> o = a
+            o = enc[i]
+        else:
+            #print(i)
+            dst, src = enc[i], org[i] 
+            if dst < src:
+                dst, src = src, dst
+            b = 1
+            while dst > 0:
+                o += b * abs(dst%2 - src%2)
+                b *= 2
+                dst //= 2
+                src //= 2
+        org.append(o)
+    return tuple(org)
+
+import unittest
+
+class TestDecodeXOR(unittest.TestCase):
+    def test(self):
+        for (enc, init), otpt in {
+                ((1, 2, 3), 1): (1, 0, 2, 1),
+                ((6, 2, 7, 3), 4): (4, 2, 0, 7, 4),
+                }.items():
+            #print(f'{enc}\n{otpt}')
+            self.assertEqual(decodeXOR(enc, init), otpt)
+ 
+unittest.main()