Linked Structures

Traverse and Print

Walk from the head pointer to null, visiting each node exactly once without random indexing.

Algorithm

The replay labels nodes by value, such as node(20), and never exposes object identity or memory addresses. This Scala DSA implementation uses the same small chain as the rest of the DSA track.

cursor A cursor reference names the node currently being visited.
null stop Traversal ends when the cursor reaches the null marker.

Basic Implementation

basic.scala
Replay: real traced execution (multi-file project)
class Node(val value: Int, var next: Node = null)

def render(head: Node): String = {
  val parts = scala.collection.mutable.ArrayBuffer[String]()
  var cursor = head
  while (cursor != null) {
    parts += cursor.value.toString
    cursor = cursor.next
  }
  parts.mkString(" -> ") + " -> null"
}

var head = new Node(10, new Node(20, new Node(30)))
println(render(head))

  1. head ← 10 -> 20 -> 30 -> null

    1class Node(val value: Int, var next: Node = null)
    values this step10 -> 20 -> 30 -> nullhead

  2. output ← 10

    5var cursor = head6while (cursor != null) {7  parts += cursor.value.toString
    values this step10outputnode(10)cursor

  3. output ← 10 -> 20

    5var cursor = head6while (cursor != null) {7  parts += cursor.value.toString
    values this step10 -> 20outputnode(20)cursor

  4. output ← 10 -> 20 -> 30 -> null

    5var cursor = head6while (cursor != null) {7  parts += cursor.value.toString
    values this step10 -> 20 -> 30 -> nulloutputnode(30)cursor

  5. stdout ← 10 -> 20 -> 30 -> null

    13var head = new Node(10, new Node(20, new Node(30)))14println(render(head))
    values this step10 -> 20 -> 30 -> nullstdout10 -> 20 -> 30 -> nulloutput

Complexity

  • Time: O(n)
  • Space: O(1)

Implementation notes

  • Keep the explicit node and pointer/reference operations; array shortcuts hide the linked-list state this lesson is meant to replay.
  • The final output prints the chain in a deterministic a -> b -> null form for cross-language comparison.