What is the time complexity of obtaining an element by index in a linked list?

The time complexity of accessing an element by index in a linked list is O(n), where n is the position of the element.

This is because a linked list does not support direct index-based access like an array. To access the element at index i, you need to traverse from the beginning of the list through i elements.

Example in Java:

class Node {
    int value;
    Node next;
}

int getElementAt(Node head, int index) {
    Node current = head;
    int count = 0;
    while (current != null) {
        if (count == index) {
            return current.value;
        }
        current = current.next;
        count++;
    }
    throw new IndexOutOfBoundsException();
}

Thus, index access in a linked list is inefficient for large index values.