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 Lua 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.lua
Replay: real traced execution (multi-file project)
local function node(value, next)
    return { value = value, next = next }
end

local function render(head)
    local parts = {}
    local cursor = head
    while cursor ~= nil do
        parts[#parts + 1] = tostring(cursor.value)
        cursor = cursor.next
    end
    return table.concat(parts, " -> ") .. " -> null"
end

local head = node(10, node(20, node(30, nil)))
print(render(head))

  1. head ← 10 -> 20 -> 30 -> null

    1local function node(value, next)2    return { value = value, next = next }
    values this step10 -> 20 -> 30 -> nullhead

  2. output ← 10

    7local cursor = head8while cursor ~= nil do9    parts[#parts + 1] = tostring(cursor.value)
    values this step10outputnode(10)cursor

  3. output ← 10 -> 20

    7local cursor = head8while cursor ~= nil do9    parts[#parts + 1] = tostring(cursor.value)
    values this step10 -> 20outputnode(20)cursor

  4. output ← 10 -> 20 -> 30 -> null

    7local cursor = head8while cursor ~= nil do9    parts[#parts + 1] = tostring(cursor.value)
    values this step10 -> 20 -> 30 -> nulloutputnode(30)cursor

  5. stdout ← 10 -> 20 -> 30 -> null

    15local head = node(10, node(20, node(30, nil)))16print(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.