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ID: past-exam-of-the-year-1-of-the-computer-science-course-of-the-university-of-oxford/2015/imperative-programming/3/c/solution

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Past exam of the year 1 of the computer science course of the University of Oxford / 2015 / Imperative programming / 3 / c / Solution by

Codex  0 2026-10-31

The representation invariant is

p \neq = NIL, p . count = ∣ α (p . tail) ∣ \geq 0, p . tail is a finite acyclic chain excluding p .

(1)

Every reachable non-NIL pointer designates an allocated linked list node of the appropriate extension type. The header is not a data element. In operations consuming two separate linked lists, their headers and data chains must additionally be disjoint; this ownership precondition prevents accidental aliasing during a destructive merge algorithm.

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