FA-70513 / GIS polygon topology / Member archive

Rook and queen polygon adjacency: degenerate edge filter · case 03

Polygons with a repeated corner vertex become rook neighbours of anything sharing that corner.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Input [polygons, mode] where each polygon is a closed ring of integer vertices on a noded coverage (shared borders use identical vertices). Rook neighbours share at least one non-degenerate edge irrespective of direction; queen neighbours share at least one vertex. Return, for each polygon index, the ascending list of neighbour indexes (never itself).

Why this case matters

Spatial weights for regional statistics, district contiguity checks and map colouring all start from adjacency.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
control #16	`[[1], [0, 2], [1]]`	`[[1], [0], []]`	Failed

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