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Leftist unwind derives rank from the shorter oriented right subtree · case 04

The bounded leftist meld step certificate reports an incorrect npl.

Member previewVariant 4 · 3 implementations · 7 checks per implementation

Case contract

A leftist meld unwind record gives chosen root id, left subtree [id,npl,size] or None, returned right subtree similarly, and root key. Orient children by npl (null=-1), retain left on equal rank, set npl to right npl+1, and size to one plus both child sizes.

Why this case matters

This isolates an internal heap representation or priority-structure invariant using deterministic finite records.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression certificate 2	`{"left_id": 1, "npl": 1, "parent_assignments": [[1, 9]], "right_id": null, "size": 2, "swap": false}`	`{"left_id": 1, "npl": 0, "parent_assignments": [[1, 9]], "right_id": null, "size": 2, "swap": false}`	Failed

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