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### 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()
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