How to evaluate the algorithmic complexity of updating an element in a linked list?

Updating an element in a linked list usually requires first finding that element, then changing its value.

• If you have a pointer or reference to the desired node, updating the value is an O(1) operation.
• If you need to find the element by index or value first, the search takes O(n), where n is the number of elements in the list.

Example in Dart (Flutter):

class Node {
  int value;
  Node? next;

  Node(this.value);
}

void updateNodeValue(Node head, int index, int newValue) {
  Node? current = head;
  int i = 0;
  while (current != null && i < index) {
    current = current.next;
    i++;
  }
  if (current != null) {
    current.value = newValue; // O(1) update
  }
}

In total, the overall complexity of updating an element by index is O(n), if there is no direct access to the node.