Update 'Linked List Cycle'

Author: nickolashkraus

README.md

@@ -20,6 +20,8 @@ A collection of LeetCode solutions
 
 [Invert Binary Tree](./src/invert_binary_tree.py)
 
+[Linked List Cycle](./src/linked_list_cycle.py)
+
 [Maximum Depth of Binary Tree](./src/maximum_depth_of_binary_tree.py)
 
 [Maximum Subarray](./src/maximum_subarray.py)

src/linked_list_cycle.py

@@ -9,6 +9,8 @@
     linked list. This algorithm can also be used for directed graphs.
 
     See: https://en.wikipedia.org/wiki/Cycle_detection
+
+This solution has O(n) runtime complexity and O(1) space complexity.
 """
 
 from src.classes import ListNode
@@ -26,7 +28,7 @@ def hasCycle(self, head: ListNode | None) -> bool:
             return False
 
         # The algorithm maintains two pointers into the given sequence, one
-        # (the tortoise) at xi, and the other (the hare) at x2i. At each step
+        # (the tortoise) at xᵢ, and the other (the hare) at x₂ᵢ. At each step
         # of the algorithm, it increases i by one, moving the tortoise one step
         # forward and the hare two steps forward in the sequence, and then
         # compares the sequence values at these two pointers. The smallest