Most Difficult Problem Ever
Prior to the discovery of new copies of the Igo Hatsuyoron, one might have thought that Xuanxuan Qijing Problem 35, nicknamed by the French master as "the emperor of life and death problems", as the most difficult problem ever.
After the discovery of new copies of the Igo Hatsuyoron in the 1980's, it is widely believed that this is the most difficult problem ever. Composed by Dosetsu himself, it is in the words of Fujisawa Shuko, who solved it with the assistance of some of his students), "a lifetime masterpiece, with elegant shapes, a striking novelty of the theme, a precise balance of the fights, etc."
/Shuko's Solution ("classic" 1982 solution until move 70, somewhat outdated)
/Three Amateurs Solution (newer solution, also partly validated by professional Chinese research)
- The Most Difficult Go Problem Ever, Go World Number 29, Autumn 1982, pages 43 and 47-49.
- ''The Most Difficult Go Problem Ever'', Brett und Stein Verlag 2011. This book presents the most profound analysis of the famous problem of the Igo Hatsuyoron. It summarizes the early research and reveals the latest findings, apparently invalidating the known solutions. It has about 300 solution diagrams, and a further 50 explanatory diagrams. It is based on a subset of the diagrams from the DGoZ web-site mentioned next.
- The Deutsche Go Zeitung has a far more detailed discussion of The really most difficult Go problem ever, which has well over 2,000 diagrams, over about 500 A4 pages, as well as SGF sources, which include most established variations. All versions use the same diagrams. The main version is in German, with a good parallel (human-mediated) English translation. The Japanese, and Chinese, versions were obtained using BabelFish? to do the translation automatically, and are therefore somewhat flawed. This site is being updated and improved quite actively (as of August 2011). It contains an introduction to the problem and an overview of the key-results, in historical order (in German and English only). In February 2011 there was added the fourth edition of a supplement of over 1,000 variations (on amateur kyu level only) after the "bad-shape" move in the top right corner, which is suspected to possibly win the game again for Black.
- There is an interactive version of the Deutsche Go Zeitung analysis (mentioned above), which includes the English-language commentary (as of June 2008), and the record (without comments) dated January 2011. It uses the brilliant free tool EidoGo. You can experiment with your own variations, and save the changes as a standard SGF file.
- A French website on this most difficult problem including the "classical" solution (which cannot be regarded correct anymore).
- Better still is Denis Feldmann's Dosetsu problem which links to an animated solution (which cannot be regarded correct either).
- Consider doing google searches for "120" (the problem number) and "hatsuyoron" (or the Japanese, Chinese, or Korean equivalents -- see IgoHatsuyoron). For example this could lead to finding another animated solution
Bob McGuigan: In another amazing whole-board problem, composed by Dosaku or perhaps Dosetsu, Black captures 72 stones but is unable to make a living group. I don't know of an online source but it is given as problem 20 in Nakayama Noriyuki's Treasure Chest Enigma.
f3etoiles It is online, on the site of goproblems.com, and Nakayama attributed it to Dosaku (but he may be a little bit biased in his judgment :-)) While we are on it, the same site has also the Dosetsu problem (with a Java solution, but I believe there are some mistakes in it, and it doesn't show the 1 point victory), and another incredible full-board thing, called No Man's Land.
Possibly the ultimate "most difficult problem ever" is: starting from an empty 19x19 board, Black to win. Currently nobody has the solution, otherwise Go would be a solved game. This problem is also often circulated as a joke.