FA-82910 / Go territory scoring / Member archive

Ko ban is set when the capturing stone joins a friendly chain · case 05

A single-stone capture by a connected stone forbids an immediate recapture that is actually legal.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

Input [board_after_move, row, col, captured_points]. A ko ban point exists only when exactly one stone was captured, the played stone has no friendly orthogonal neighbour, and it has exactly one liberty. Return the captured point or None.

Why this case matters

Go servers and scoring tools compute this value automatically; a wrong answer changes a game result.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
ko point case 0	`[0, 1]`	`null`	Failed

MEMBER ARCHIVE

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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