diff --git a/linked_lists/README.md b/linked_lists/README.md
index 2057935..51ddc66 100644
--- a/linked_lists/README.md
+++ b/linked_lists/README.md
@@ -5,6 +5,13 @@
 * unlike an array, a list does not provide constant time access to an index (as it needs to interact through all k elements), however addition and removal of elements are constant time.
 * to remove a node you set `prev.next` equal to `node.next`. if it's a double list, you also update `node.next` with `node.next.prev` to `node.prev` (and deallocate the memory).
 
+<br>
+
+### detecting cycles
+
+<br>
+
+* can be done with hash table or the two-pointer technique, where if there is no cycle, the faster pointer (going 2 steps) will stop at the end of the list, but if there is a cycle, the fast pointer will eventually meet the slow pointer (going 1 step). if there is no cycle, the faster pointer takes `N/2` to reach the end of the list (`N` being the length).
 
 <br>