E_ca_ation 2: The Lost Ri_er
(Eingestellt am 5. Juni 2021, 07:39 Uhr von SSG)
It's hard to believe this was once the lushest river valley for a thousand miles. Glancing around the dusty wasteland, you can just make out a few stony outcrops that may once have sat on the river bank. If you're going to find the ancient barque that sank here, you'll need to find a way to carefully trace the river's course.
Normal sudoku rules apply
River (snake): There is a one cell wide path through the grid, tracing the river's former course. The river entered and exited the grid along different edges, and it never touched itself, even diagonally. The gray cells are stone outcrops that formed part of the river's banks. The digit placed in an outcrop cell must equal the number of adjacent river cells, including diagonals. All possible outcrop cells are given.
XV: Pairs of cells connected by an X must sum to 10. Pairs connected by a V must sum to 5. There is one pair of river cells, representing the location of the barque, for which no V is given. Every other possible X or V connecting two cells, each of which is either a river cell or an outcrop cell, is given. Xs and Vs that connect to cells that are neither river nor outcrop may or may not be given.
f-puzzles: https://f-puzzles.com/?id=y4saee9d
CTC: https://tinyurl.com/4a57yn4k
Lösungscode: Column 8
Kommentare
am 21. September 2022, 20:59 Uhr von SSG
Clarification of the XV rule and formatting improvements.
am 21. September 2022, 16:38 Uhr von codewizard
@h5663454
I eventually solved it, and the rules (or interpretation thereof) that worked for me was that:
- The negative constraint for both X and V, applies to pairs of cells that are EITHER river or given/gray outcrops (not any adjacent non-river cell). Ie. combinations: river+river, river+outcrop, outcrop+outcrop.
- The exception is only on pairs of BOTH RIVER cells, adding to 5. As the rules say, there is exactly one such pair (which don't have a given V).
There might be additional constraints that makes it easier, but that was what was required for me. I started by just assuming it applied to river+river and outcrop+outcrop (outcrop=gray). Then grinded to a halt and then added river+outcrop as well.
I must say that this is a really beautiful and lovely puzzle, once you don't feel unsure about which assumptions you can make :)
@SSG I would suggest changing "cells that are each" to "cells that are either ..., or both". Also clarifying that "outcrop" means only the given gray cells. Strictly the rules says that, because "all possible outcrops are given", BUT the given X's and V's include cells that are not necessarily river or given outcrops, so appears to contradict that.
-Wow. I have to admit I didn't expect to ever see activity on this one again. This was only the third puzzle I ever constructed; and, in retrospect, the rules are just too complicated, which is why I was never able to find a way to write them that didn't end up confusing people. (My intent in constructing the puzzle was that there would be a total negative constraint on XVs except the one hidden V; but, I couldn't find a way to do that without the puzzle becoming *very* uninteresting.) Anyway, your ultimate interpretation is the intended one; and, I'm glad you enjoyed the puzzle once you were able to get to that! -SSG
am 21. September 2022, 16:18 Uhr von h5663454
I'm sorry, but I don't understand your description of the xv rule. It's so vaguely described that I'm not sure if there is a negative constraint.
Although it has been a long time since the puzzle was released, I hope you will see my suggestion and revise the description of the xv rules to make it clearer and easier to understand.
am 21. September 2022, 14:07 Uhr von codewizard
I think this is a really nice puzzle (so far - i'm mid solve at the moment). I do have to say that the negative constraints on the X's and V's are a bit unclear and ambiguous, to me. In the "pair of cells that are each river or outcrop", I think the word "each" is strange. Would expect it to be "both", "either (but not both)" or "any of". It could be interpreted a few different ways:
a) If a pair adding to 10 consists of two river cells, OR two outcrop cells, an X is given.
b) If a pair adding to 10 consists of exactly one river and exactly one outcrop, an X is given.
c) If a pair adding to 10 consists of cells that are either river or outcrop (they can be same or different), an X is given. I suppose this would mean more or less all pairs in the grid.
I've tried to guess and tested a bit but run into contradictions - but that could be because of some "upstream" (haha) mistake...
EDIT: and/or there might be an additional layer of confusion (for me) what counts as an "outcrop" or "stone outcrops", if there is a difference. If "outcrops" are only the given gray cells, or any cell adjacent to a river cell.
am 17. Oktober 2021, 00:33 Uhr von uvo_mod
Labels angepasst.
am 3. September 2021, 21:15 Uhr von SSG
Added CTC app link.
am 10. August 2021, 08:16 Uhr von SSG
Reevaluated the difficulty rating.
am 10. Juni 2021, 16:46 Uhr von nordloc
I'm not good at these path puzzles so I probably missed some important logic but this seemed a lot harder than 2 stars to me. After a gentle start I got stuck for a long time.
