## PINDOH.com - New logic puzzle site

For fans of all other kinds of logic puzzles

### PINDOH.com - New logic puzzle site

Hi All,

Check out PINDOH.com - great new logic puzzle!

smith22

Posts: 2
Joined: 17 October 2012

### Re: PINDOH.com - New logic puzzle site

Has something in common with Mastermind. Very enjoyable!
evert

Posts: 186
Joined: 26 August 2005

### Re: PINDOH.com - New logic puzzle site

or should we say is exactly the same as "Mastermind".
is just numbers instead of colors.
haven't play that game for decades.
7b53
2012 Supporter

Posts: 156
Joined: 01 January 2012
Location: New York

### Re: PINDOH.com - New logic puzzle site

He-he, I coded the Bulls and cows version of this problem in fortran in 1987 and found the best strategy is always to ask for a combination that satisfies all previously collected constraints.

Really enjoyable!
dobrichev
2016 Supporter

Posts: 1516
Joined: 24 May 2010

### Re: PINDOH.com - New logic puzzle site

Hi, smith22!
smith22 wrote:Check out PINDOH.com - great new logic puzzle!

Interesting idea - to treat sequence of turns in "Bulls and cows" game as logical puzzle. I don't understand in what way should one treat answers when a turn has repetitive digits. For example, does answer "2" to "3384" turn imply that "3" can be alone right digit (counted twice)?

For dobrichev. Yes, I played "Bulls and cows" in student years. Nice game! I found strategy "always to ask for a combination that satisfies all previously collected constraints" too. It worked well, but I am not sure - is it really best strategy? Thanks for Wikipedia link!

Serg
Serg
2018 Supporter

Posts: 572
Joined: 01 June 2010
Location: Russia

### Re: PINDOH.com - New logic puzzle site

Serg wrote:... is it really best strategy?

I can't prove this in mathematical sense, but there are no much alternative strategies.
There is a broken link to a pdf ("Optimal algorithms for bulls and cows game")in the Wikipedia page. The document from the next link looks far too much essential with my (non-)installed fonts.

Assuming no repetition of digits in queries and the target,
- first query can be always 1234 (due to isomorphism);
- last query (max 7-th) obviously should satisfy constraints.
In between there are max 5 queries with < 1K possibilities each. Someone can attack these < (10^3)^5 = 10^15 approaches. Surely there are more symmetries such as independent order of some of the queries (if not all).
dobrichev
2016 Supporter

Posts: 1516
Joined: 24 May 2010

### Re: PINDOH.com - New logic puzzle site

Serg wrote:I don't understand in what way should one treat answers when a turn has repetitive digits. For example, does answer "2" to "3384" turn imply that "3" can be alone right digit (counted twice)?

Wikipedia wrote:If there are duplicate colours in the guess, they cannot all be awarded a key peg unless they correspond to the same number of duplicate colours in the hidden code. For example, if the hidden code is white-white-black-black and the player guesses white-white-white-black, the codemaker will award two colored key pegs for the two correct whites, nothing for the third white as there is not a third white in the code, and a colored key peg for the black. No indication is given of the fact that the code also includes a second black.

Source
evert

Posts: 186
Joined: 26 August 2005

### Re: PINDOH.com - New logic puzzle site

dobrichev wrote:He-he, I coded the Bulls and cows version of this problem in fortran in 1987 and found the best strategy is always to ask for a combination that satisfies all previously collected constraints.

Really enjoyable!

Is that still the best strategy against a computer program that is allowed to adapt 'the secret key' after each guess? And give feedback as to end up with the largest set of remaining options?
evert

Posts: 186
Joined: 26 August 2005

### Re: PINDOH.com - New logic puzzle site

evert wrote:Is that still the best strategy against a computer program that is allowed to adapt 'the secret key' after each guess? And give feedback as to end up with the largest set of remaining options?

I've written a Java applet based on this idea.
evert

Posts: 186
Joined: 26 August 2005