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Euler trail feasibility checks parity without edge connectivity · case 05

Euler trail feasibility checks parity without edge connectivity.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

Return whether an undirected multigraph has a trail using every edge exactly once. Zero edges are feasible; isolated vertices do not constrain the trail. Self loops contribute degree two.

Why this case matters

A deterministic in-memory graph model isolates this invariant; no large-graph performance or production graph engine behavior is claimed.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
two disconnected loops	`true`	`false`	Failed

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