vault backup: 2022-09-20 14:26:40

OJ notes/pages/Leetcode Reverse-Linked-List.md

@@ -102,7 +102,12 @@ The iteration method use two pointers:
 - one that points to the new head, as an anchor
 - The other one points to nodes we need to iterate over:
 
+The iterator **has** to be pointing to head, and use 
+`cur->next` instead of directly using cur, otherwise will
+lead to strange loops or bugs.
 
+The pointer moves by `cur->next = cur->next->next`, it 
+represents the head element.
 
 ### Solution
 
@@ -123,6 +128,7 @@ public:
       // Move cur->next after pre.
       pre->next = cur->next;
       // Fix pointers, because cur->next is unchanged when changing position.
+			// This part is important, must use cur->next.
       cur->next = cur->next->next;
       pre->next->next = temp;
     }