Sort the linked list using quicksort technique

Author: Darpan-Balar

Sorting Algorithims/quicksort_linkedlist.py

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+"""
+Given a linked list with head pointer, 
+sort the linked list using quicksort technique without using any extra space
+Time complexity: O(NlogN), Space complexity: O(1)
+"""
+from __future__ import annotations
+
+
+class Node:
+    def __init__(self, data: int) -> None:
+        self.data = data
+        self.next = None
+
+
+class LinkedList:
+    def __init__(self):
+        self.head = None
+
+    # method to insert nodes at the start of linkedlist
+    def insert(self, new_data: int) -> None:
+        new_node = Node(new_data)
+        new_node.next = self.head
+        self.head = new_node
+
+    # method to print the linkedlist
+    def printLL(self) -> None:
+        temp = self.head
+        if temp == None:
+            return 'Linked List is empty'
+        while temp.next:
+            print(temp.data, '->', end='')
+            temp = temp.next
+        print(temp.data)
+        return
+
+# Partition algorithm with pivot as first element
+
+
+def partition(start, end):
+    if start == None or start.next == None:
+        return start
+    prev, curr = start, start.next
+    pivot = prev.data
+    while curr != end:
+        if curr.data < pivot:
+            prev = prev.next
+            temp = prev.data
+            prev.data = curr.data
+            curr.data = temp
+        curr = curr.next
+    temp = prev.data
+    prev.data = start.data
+    start.data = temp
+    return prev
+
+
+# recursive quicksort for function calls
+def quicksort_LL(start, end):
+    if start != end:
+        pos = partition(start, end)
+        quicksort_LL(start, pos)
+        quicksort_LL(pos.next, end)
+        return
+
+
+if __name__ == "__main__":
+    ll = LinkedList()
+    print("Enter the space seperated values of numbers to be inserted in linkedlist prompted below:")
+    arr = list(map(int, input().split()))
+    for num in arr:
+        ll.insert(num)
+    print("Linkedlist before sorting:")
+    ll.printLL()
+    quicksort_LL(ll.head, None)
+    print('Linkedlist after sorting: ')
+    ll.printLL()