Add length and rotate method to linkedlist.py

easyPythonpi/methods/linkedlist.py

@@ -40,3 +40,51 @@ def display_nodes(head:'node')->'int':
         t=t.next
     print("NULL")
 
+# get length of list
+def get_linked_list_length(head:'node')->'int':
+
+    # base case
+    if head is None:
+        return 0
+
+    length, curr = 1, head
+    # loop through list to accumulate length
+    while head.next:
+        head = head.next
+        length += 1
+
+    return length
+
+# given the head of a linked list and a number n, rotate the linked list by n spaces
+def rotate_linked_list(head:'node', n:int)->'list':
+
+    # if linked list is None or length of 1 or n is negative
+    # just return head
+    if head is None or head.next is None or n <= 0:
+        return head
+
+    # get length of list
+    length = get_linked_list_length(head)
+
+    # get new tail
+    tail = head
+    while tail.next:
+        tail = tail.next
+
+    # optimize rotation to account for looping through entire list multiple times
+    n = n % length
+
+    # if n == 0, we don't need to rotate anything
+    if n == 0:
+        return head
+
+    curr = head
+    for i in range(length - n - 1):
+        curr = curr.next
+
+    # update necessary pointers
+    new_head = curr.next
+    curr.next = None
+    tail.next = head
+
+    return new_head