## Build a fewest-moves freecell solver

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8

In the game of Freecell, you are tasked with building four foundation piles in suit from ace to king, on a layout where you build downward in alternating colours. However, you can only build one card at a time, so you are given four "free cells" each of which can contain one card to help you move entire sequences. The idea is that you weave individual cards in and out of the free cells as required to help you solve the game.

Your task is to build a program that will solve these games in the fewest moves possible.

Your program will take as input a sequence of 52 cards, in the following format:

2S 9H 10C 6H 4H 7S 2D QD KD QC 10S AC ...


Which will be dealt in the initial layout in this order:

01 02 03 04 05 06 07 08
09 10 11 12 13 14 15 16
17 18 19 20 21 22 23 24
25 26 27 28 29 30 31 32
33 34 35 36 37 38 39 40
41 42 43 44 45 46 47 48
49 50 51 52


And return a list of moves to solve the game. Each move will be in this format:

• A number representing the pile number (1 through 8), or a free cell (A to D), representing the source pile.
• Another number or letter representing the destination pile or free cell, or F for the foundation of that suit.

The output will look something like this:

18 28 3A 8B 8C 85 B5 35 4F etc.


Once a card is put into the foundation, it cannot be removed. Since only one card is moved at a time, moving a sequence of 3 cards requires 5 moves, and a sequence of 5 cards requires 9 moves.

If a game is unsolvable, your program should indicate as such. However, your program must be able to solve any solvable game.

Your program will be judged on the 32,768 deals found in the original Microsoft FreeCell program. In order to be valid, your program must successfully solve every deal except deal #11,982, which is unsolvable. Your score will be the total number of moves it takes to solve these 32,767 deals, with shorter code being a tie-breaker.

A file with all the decks in the format required by the above specification is available for download here (5.00 MB file): https://github.com/joezeng/pcg-se-files/raw/master/freecell_decks

1Now I just need to nab the random number generator that they used to generate those 32,768 games. :S – Joe Z. – 2015-01-03T18:49:00.337

3

The generator is here: http://rosettacode.org/wiki/Deal_cards_for_FreeCell

– nutki – 2015-01-03T19:25:55.040

Thanks, nutki. Lemme generate a text file with the decks in them, for testing. – Joe Z. – 2015-01-04T01:37:07.043

It would be nice if your example input sequence included at least one ace. – n8chz – 2015-01-24T22:21:08.410

Oh, sorry, aces are A. – Joe Z. – 2015-01-24T23:37:20.077

A quick question: Must the code handle the free cells as four separate "slots" or can the free cells be seen as a "stack" of max 4 cards? Codewise it would be unnecessary complicated to check which of the four slots is empty when that sub-problem can be reduced to wether any of the slots is free. Output-wise, the only changes would be that putting a card to the free cell would be i.e. "1C", "2C" instead of "1C1" or "1C2" or "1C3" or "1C4", the solution would still be valid. – Lars Ebert – 2015-03-18T10:49:12.063

1That's a good point. How would you deal with the case in which, say, two cards of the same colour and number (such as 7C and 7S) are both in free cells? Then if you move from "C" to a black 8, it could be either of those two cards. – Joe Z. – 2015-03-18T15:14:56.323

I think this problem has much larger hurdles than worrying about how to golf a few more bytes due to how the free cells are treated. That could be done with a bit field showing whether a cell is occupied, or perhaps representing the free cells as a 4-byte string and searching for the first blank, or some other creative method. – GuitarPicker – 2016-07-20T12:49:38.690

1. @Lars Ebert: The free cells are no 4-card stack but four 1-card. 2. @Joe Z.: How about naming them A,B,C,D instead of C1..C4? I consider that easier to read. – Titus – 2016-07-20T13:45:19.160

@Titus That would work, actually. – Joe Z. – 2016-07-25T04:36:19.177

2You could possibly get some answers by removing the restriction that all solvable deals must be solved by the submission. Then, score based on number of deals solved, then by fewest moves. – mbomb007 – 2017-02-16T21:59:36.280

Is Freecell a solved game, at least from all valid starting positions? If so, this is... well, not trivial, but fairly simple. If not, I'd rather not spend decades proving that it's the fewest possible moves. – Fund Monica's Lawsuit – 2017-03-02T01:06:18.503

Of interest: FreeCell solutions to 1000000 games

– Guy Coder – 2017-03-15T19:15:17.370

It's hard to understand from your description - how does that array relate to any of the piles? Do the rows (or the columns) each represent a pile? Or something else. It's also very unclear what the valid moves are - I think it would help to show some examples (with "before" and "after" grids) showing representative valid and invalid moves. It might help if you can link to a reference site, as it's probably not a very widely played variant. – Toby Speight – 2017-04-06T13:15:05.853

Freecell is a solved game, thus it is known that there are unwinnable layouts. E.g. seed 11982 on the Windows version. – Draco18s no longer trusts SE – 2017-05-10T20:05:20.237

1can the cards be 0-Indexed? – tuskiomi – 2017-07-11T15:45:31.247

Can the "10" card be represented by a T instead of a 10? That way, each individual card (AS, 2C) is two characters (TH) instead of sometimes three (10H). – Brian J – 2017-07-25T16:15:02.960

@mbomb007 nah. Been there done this – Christopher – 2017-08-21T00:12:14.667

Do we really need to solve every one? It took 2 days to solve the first ~700 – Christopher – 2017-09-06T21:50:30.103

Here´s a solution (including C source and a JavaScript port): http://fc-solve.shlomifish.org/. Idk if it´s really fewest moves, but it´s pretty good.

– Titus – 2017-09-11T20:52:46.650

22

# C 64,643 bytes, Score: ~6.5 million

The following Stack Snippet (courtesy of Mego) outputs all of the code as a single standalone C file:

\$("#a").text(pako.inflate(atob('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'), {to: 'string'}));
<script src="https://cdn.rawgit.com/nodeca/pako/master/dist/pako.min.js"></script>
<pre id="a">

</pre>

Download the original source here. Use GCC and run make then using the guideline in the readme.

My formatting is bad (all the different files are in one code block) and this could be golfed more (12k bytes tho). Any help would be loved!

Some of the code is not mine. I used it from a un-copyrighted source. I however fixed the input/output method to be within the challenge (a long task since I am horrible at C (5ish hours)). I also had to re-write much of the code and debug everything. Many thanks to my Dad for helping out and being a rubber duck (and pointing out my memory management errors) and for everyone on TNB who dealt with my angry rants about segfaults and C.

You may be able to use this to get around the answer length restriction and have all of your code within the answer, rather than needing an external download.

– Mego – 2018-01-02T22:38:06.563

@Mego i mean yeah but it is in several files – Christopher – 2018-01-02T23:15:33.977

It's easy to combine multiple C files into a single one. – Mego – 2018-01-02T23:34:30.560

Here is a stack snippet that shows the code combined into a single file. – Mego – 2018-01-02T23:56:37.153

@mego can you edit that in? On mobile – Christopher – 2018-01-03T14:51:59.687