Linked lists are difficult at first because students must reason about references instead of indexes. Arrays let you jump to position 4. Linked lists require a chain of nodes, and each node points to the next one.
Draw the nodes
Every linked list problem becomes easier when students draw boxes for nodes and arrows for references. The drawing should include the head reference, any temporary reference, and the next fields that are being changed.
class Node
{
private int data;
private Node next;
}Traversal pattern
A traversal usually starts at the head and advances one node at a time. The loop condition should be chosen carefully. If the code needs to inspect the current node, use current != null. If the code needs to look ahead, use current.getNext() != null.
Insertion needs order
When inserting a node, connect the new node before breaking the old connection. If the order is wrong, part of the list can become unreachable.
Deletion needs the previous node
To remove a middle node, the code usually needs access to the node before it. That previous node can skip over the removed node by pointing to the removed node's next reference.
Common mistakes
- Losing the rest of the list by overwriting a reference too early.
- Forgetting special cases for an empty list or one-node list.
- Using array-style thinking where indexes do not exist.
- Stopping one node too soon or one node too late.
The key habit is simple: do not write pointer code blind. Draw the before state, the update, and the after state.