Merge pull request #10874 from pauloscustodio/master

Add Python solution to challenge 067

1 files changed, 39 insertions, 0 deletions

diff --git a/challenge-068/paulo-custodio/python/ch-2.py b/challenge-068/paulo-custodio/python/ch-2.py
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+++ b/challenge-068/paulo-custodio/python/ch-2.py
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+#!/usr/bin/env python3
+
+# Challenge 068
+#
+# TASK #2 > Reorder List
+# Submitted by: Mohammad S Anwar
+# You are given a singly linked list $L as below:
+#
+# L0 ?  L1 ?  ... ?  Ln-1 ?  Ln
+# Write a script to reorder list as below:
+#
+# L0 ?  Ln ?  L1 ?  Ln-1 ?  L2 ?  Ln-2 ?
+# You are ONLY allowed to do this in-place without altering the nodes' values.
+#
+# Example
+# Input:  1 ?  2 ?  3 ?  4
+# Output: 1 ?  4 ?  2 ?  3
+
+import unittest
+
+def reorder_list(l):
+    # get second element
+    tail = l[1]
+    # get and remove last element
+    p = tail
+    last = None
+    while len(p) > 1:
+        last = p
+        p = p[1]
+    eln = last.pop()
+
+    return [l[0], [eln[0], tail]]
+
+class TestReorderList(unittest.TestCase):
+    def test_reorder_list(self):
+        self.assertEqual(reorder_list([1, [2, [3, [4]]]]), [1, [4, [2, [3]]]])
+
+if __name__ == '__main__':
+    unittest.main()