Merge pull request #223 from Varalakshmi2354/potdsoln

POTD_29_OCT_2024_quicksort on linked list

october_2024/GFG_POTD_29_OCT_2024.py

@@ -0,0 +1,50 @@
+def quickSort(head):
+    if head is None or head.next is None:
+        return head
+
+    def partition(head, end):
+        pivot = head.data
+        lesser_head = lesser_tail = Node(0)
+        equal_head = equal_tail = Node(0)
+        greater_head = greater_tail = Node(0)
+
+        current = head
+        while current != end:
+            if current.data < pivot:
+                lesser_tail.next = current
+                lesser_tail = lesser_tail.next
+            elif current.data == pivot:
+                equal_tail.next = current
+                equal_tail = equal_tail.next
+            else:
+                greater_tail.next = current
+                greater_tail = greater_tail.next
+            current = current.next
+
+
+        lesser_tail.next = equal_tail.next = greater_tail.next = None
+
+        return lesser_head.next, equal_head.next, greater_head.next
+
+    def concatenate(lesser, equal, greater):
+        dummy_head = Node(0)
+        current = dummy_head
+
+        current.next = lesser
+        while current.next:
+            current = current.next
+
+        current.next = equal
+        while current.next:
+            current = current.next
+
+        current.next = greater
+        return dummy_head.next
+
+    lesser, equal, greater = partition(head, None)
+
+    lesser = quickSort(lesser)
+    greater = quickSort(greater)
+
+    sorted_head = concatenate(lesser, equal, greater)
+    return sorted_head