### Dr. Sudoku Prescribes #19 – Cave

PDF

or solve online (using our beta test of Penpa-Edit tools; use tab to shift between shading mode and the linex mode where left click+drag draws lines and right click marks X’s)

Theme: Ascending/Descending Diagonal

Rules: Standard Cave rules.

Answer String: Enter the length in cells of each of the cave segments from left to right for the marked rows, starting at the top. Separate each row’s entry with a comma.

Time Standard: Cave Master = 1:00, Expert = 3:00, Novice = 10:00

Solution: PDF

Note: Follow this link for other Cave variations and this link for other classic Caves. If you are new to this puzzle type, here are our easiest Cave Puzzles to get started on.

• skynet says:

Hi motris another new puzzle i m geting introduced to..Is there any site which shows how to start doing this puzzle just like nikoli for nurikabe? i saw in nikoli there was no starting for cave..I am not able to make a start in this puzzle…can you post a link or something on how to start this puzzle?

• skynet says:

Can someone post a link on how to solve a cave??i would be very grateful…

• drsudoku says:

Giovanni’s shared a good link which says a lot more, but unfortunately for you does not show a lot more in pictures. I can’t find anything with solving images mid-process on line to help.

Here are a few starting rules to help on this puzzle:

A 2 two cells away from another number cannot connect to that number. So mark that middle cell as “not cave”. Doing this in the lower-left corner marks a lot of used/unused cells very fast as the 5 hits the 569, and then the 6 and 9 go over to the right 1 and 4 more cells respectively.

A trickier step is that a 2 that is diagonally adjacent to another number must go towards that number. In this puzzle, in the top right, the 24 has to have the 2 connection either up or to the right. If it went down or left, you would shade in unused cells between the 2 and 4 that would make it impossible to get one group without enclosed cells. This is what I sometimes call the “no checker-board” rule in 2×2 square. It has a more formal mathematical origin but you should keep it in mind.

• Giovanni P. says:

Hi skynet,

motris did a “Better Know a USPC” post a while back with some tips on common Cave/Corral strategies: http://motris.livejournal.com/145824.html

Basically, it boils down to marking what squares small or large numbers can/can not see, making sure any squares you know are outside the loop reach the border, and avoid any 2×2 “checkerboard” arrangements. The link explains it a little more clearly than I do.

As for this puzzle, all three strategies can be useful at some points in the solve. My advice would be to find a start on the left side of the puzzle. If you use the strategies motris outlines, you can find one or two possible openings immediately.

By the way, the “required fields” in the Reply area should probably be marked with as asterisk or something.

• skynet says:

Thnks a lot motris and Giovanni…I got the required start that i was looking for by seeing the tips above…and i have completed the puzzle..thnks again !!!
Puzzles are not something like sudokus where the basic rule is the same..so even if a 1000 variants come up in sudokus can easily complete a sudoku..not the case unfotunately with puzzles..
My aim this year is to do all the puzzles this site throws up because the quality is very high in this blog .
I also take this time to thank motris for suggesting me tetsuya nishio’s books like hot and spicy sudoku and even higher sudoku.I am glad that i took his advice and bought these 2 excellent books. Excellent quality sudokus in both.I happened to see during that time a book co-authored by motris ..elegant challenges..I m interested to buy it too….Motris can you kindly say me the variants that you have conjured up in that nice book ?It would be of a great help to me to know beforehand abt the variants that come up in that book..

• mokrton says:

9:18

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