DSA Basics: Singly Linked List

A singly linked list is a chain of nodes.

Each node stores a value and a pointer to the next node.

head -> [12 | next] -> [24 | next] -> [36 | null]

Why linked lists exist

Arrays store values next to each other in memory. Linked lists connect values through references.

That means a linked list can insert or remove nodes without shifting every later value, but it cannot jump directly to index 20.

Core operations

• Traverse from head
• Insert at the beginning
• Insert after a known node
• Delete after finding a node
• Search by walking node by node

Traversal

function printList(head) {
	let current = head;

	while (current !== null) {
		console.log(current.value);
		current = current.next;
	}
}

Common mistakes

• Losing the rest of the list while changing links
• Forgetting to update head
• Not handling an empty list
• Infinite loops caused by accidental cycles

Complexity

• Access by index: O(n)
• Search: O(n)
• Insert at head: O(1)
• Delete known next node: O(1)

Practice links

• LeetCode Linked List problems
• NeetCode practice roadmap

Use the visualizer below to move through a linked list one node at a time.