River crossing Puzzle 1

    Five people - Alice, Bob, Carlos, Diana, and Elena - must cross a river in a small boat. The boat can only hold three people at a time. The following conditions apply:

* Alice refuses to be in the boat with Carlos

* Bob and Diana must travel together if either one is in the boat

* Elena can only operate the boat when Carlos is not present

* At least one person in each crossing must know how to operate the boat

* Only Bob, Carlos, and Elena know how to operate the boat

Infer an efficient plan.

Try ChatGPT o1 reasoning, verified by Claude using REACT (it works.)

Try ChatGPT 4o, failure verified by Claude

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