solve : reorder-list

Author: SamTheKorean

reorder-list/samthekorean.py

@@ -0,0 +1,32 @@
+# TC : O(n)
+# SC : O(m) m being the sum of deque and dummy nodes
+class Solution:
+    def reorderList(self, head: Optional[ListNode]) -> None:
+        if not head or not head.next or not head.next.next:
+            return
+
+        # Step 1: Use a deque to collect nodes
+        d = deque()
+        current = head
+        while current:
+            d.append(current)
+            current = current.next
+
+        # Step 2: Reorder the list using deque
+        dummy = ListNode(0)  # Dummy node with value 0
+        current = dummy
+        toggle = True
+
+        while d:
+            if toggle:
+                current.next = d.popleft()  # Append from the front of the deque
+            else:
+                current.next = d.pop()  # Append from the back of the deque
+            current = current.next
+            toggle = not toggle
+
+        # Step 3: Ensure the last node points to None
+        current.next = None
+
+        # Step 4: Reassign head to point to the new reordered list
+        head = dummy.next