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0148-sort-list/0148-sort-list.py

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+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def sortList(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        # Base case: len <= 2
+        if head == None or head.next == None:
+            return head
+        elif head.next.next == None:
+            if head.val > head.next.val:
+                large = head
+                small = head.next
+
+                small.next = large
+                large.next = None
+                return small
+            return head
+
+        # Find middle node
+        mid = head
+        end = head.next
+        while end.next is not None and end.next.next is not None:
+            mid = mid.next
+            end = end.next.next
+    
+        # Detach lists
+        secondHead = mid.next
+        mid.next = None
+
+        # Merge two sorted linked lists
+        sortedLeft = self.sortList(head)
+        sortedRight = self.sortList(secondHead)
+
+        isLeftLower = sortedLeft.val < sortedRight.val
+        mergeHead = sortedLeft if isLeftLower else sortedRight
+        currentHead = mergeHead
+
+        sortedLeft = sortedLeft.next if isLeftLower else sortedLeft
+        sortedRight = sortedRight if isLeftLower else sortedRight.next
+        while sortedLeft is not None and sortedRight is not None:
+            isLeftLower = sortedLeft.val < sortedRight.val
+
+            lowestNode = sortedLeft if isLeftLower else sortedRight
+            sortedLeft = sortedLeft.next if isLeftLower else sortedLeft
+            sortedRight = sortedRight if isLeftLower else sortedRight.next
+            currentHead.next = lowestNode
+            currentHead = currentHead.next
+
+        currentHead.next = sortedLeft if sortedLeft is not None else sortedRight
+
+        return mergeHead