River crossing Puzzle 2

 渡河問題2 (statement)，Problem via 許元銘

結果視覺化

Visualization to verify results

Claude solution non-reasoning (incorrect)

Sonnet 4 extended fails

Reasons: sometimes one of the constraints was disregarded. 2

ChatGPT 5 works 3/5.  (Two claimed to use Python code execution. One is correct. The other is not. Therefore, is it true code was generated and then executed?) 1, *2x, 3, 4x, *5

Grok

Even reasoning mode of Grok fails.

Code Gen

Use ChatGPT 5 to generate BFS search

 search that works

Use Claude second time to generate A*

 it takes 15 steps. (thanks to the python code generated by Claude)

python code

another 15-step solution

yet another 15-step

one more 15-step

last 15-step