Merge sorted lists

Combine two ascending linked lists by repeatedly taking the smaller current head.

Remember: Take the smaller head.

Example: 1 → 3 and 2 → 4 become 1 → 2 → 3 → 4.

Time: O(n + m). Auxiliary space: O(1).

Formula: take the smaller current head

Both lists must be ascending. Stable ties come from list A first. O(n + m) time; O(1) pointer workspace, excluding output/visualization.

Complexities describe the underlying algorithm; tutorial snapshots and rendering can use additional resources.

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