diff --git a/0206_reverse_linked_list/reverse_list.c b/0206_reverse_linked_list/reverse_list.c
index 9031752..22c65bd 100644
--- a/0206_reverse_linked_list/reverse_list.c
+++ b/0206_reverse_linked_list/reverse_list.c
@@ -31,8 +31,10 @@ struct ListNode *reverseList(struct ListNode *head)
     struct ListNode *prev = NULL;
     struct ListNode *p = head;
     while (p != NULL) {
+        /* prev <- p <- q */
         struct ListNode *q = p->next;
         p->next = prev;
+        /* step */
         prev = p;
         p = q;
     }
diff --git a/0206_reverse_linked_list/reverse_list.cc b/0206_reverse_linked_list/reverse_list.cc
index 212aee6..426a748 100644
--- a/0206_reverse_linked_list/reverse_list.cc
+++ b/0206_reverse_linked_list/reverse_list.cc
@@ -18,8 +18,10 @@ class Solution {
         ListNode *prev = nullptr;
         ListNode *p = head;
         while (p != nullptr) {
+            // prev <- p <- q
             ListNode *q = p->next;
             p->next = prev;
+            // step
             prev = p;
             p = q;
         }