Practice Design Linked List

MyLinkedList starts empty and uses zero-based indices. get(index) returns a node value or -1 for an invalid index. addAtHead(val) and addAtTail(val) insert at the ends. addAtIndex(index,val) inserts before that position, appends at length, and does nothing beyond length. deleteAtIndex(index) removes only a valid position. Implement nodes yourself rather than using a linked-list library. Practice approach: A sentinel head simplifies insertions and deletions at index zero. Track size for bounds checks and locate the predecessor before changing links. Check empty-list operations and insertion exactly at the tail. A singly linked implementation uses O(n) indexed operations and O(n) storage.