Create Linked List

Given a slice of values, build a singly linked list containing those values in order and return its head.

createLinkedList(values)

Input format: space-separated values. Output the resulting list (or empty line for an empty input).

Examples

[1, 2, 3]   // → 1 → 2 → 3
[9]         // → 9
[]          // → (empty)

Walkthrough

Thinking it through

Building a list from values sounds trivial, but there's a bookkeeping trap: the first node you create has nothing to attach to yet. If your rule is always "attach after the current tail," you need a tail before you've built anything — including before the first node exists.

The dummy-head trick

Invent a placeholder node that represents no real value, and treat it as sitting right before the list starts. Now every value, including the first, follows the same rule: create a node, attach it after the current tail, move the tail forward. No special case for the first element — the dummy absorbs it.

Building the list

Create the dummy node; set tail to it.
For each value: create a node, link it as tail.next, move tail to the new node.
Return dummy.next — the real head, skipping the placeholder.

Why this matters and what it prevents

Without the dummy, you'd need an "is this the first node?" check every iteration, or separate logic for setting the head versus appending. The dummy trades that conditional complexity for one throwaway node — cheap and uniform. Whenever you catch yourself writing "if this is the first item, do X, otherwise Y," consider a dummy node instead so X and Y become the same code path.

Each value costs constant work — allocate a node, relink two pointers — so it's O(n) time and O(n) space for the resulting list.

main.py

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Console

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