Dr. Sudoku Prescribes #94 – Battleships
or solve online (using our beta test of Penpa-Edit tools; use tab to alternate between ship placement and shading modes. In ship placement mode, right click gives sea, left click gives circle/square, left click and drag for rounded ships.)
Theme: Shipping Lanes
Rules: Standard Battleships rules.
Answer String: For each row from top to bottom, enter the number of the first column from the left where a ship segment appears. If the row is empty, enter 0. Enter these numbers as a single string with no separators.
Time Standards (highlight to view): Grandmaster = 2:30, Master = 5:15, Expert = 10:30
Solution: PDF
Using uniqueness I found A solution very quick,
but proving that this must be THE solution is not so trivial.
Maybe I missed sth…
I solved quickly using what felt like gut instinct, but going back to prove my solution, here’s what I found (with rot13 spoilers):
– The only differences between the “shipping lanes” ner gung sbhe bs gurz unir fdhnerf oybpxrq bss. Fb, lbh svefg cebir jung gur svir ynarf zhfg ybbx yvxr, gura cynpr gurz va gur tevq ynfg.
– Rows 3 and 8 zhfg pbagnva bayl fuvcf bs 3 havgf be ybatre. Bgurejvfr gurer jvyy or abjurer gb svg gubfr fuvcf.
– Placing the 4 unit ship vagb gur gbc unys bs gur tevq dhvpxyl yrnqf gb gebhoyr va gur sbez bs univat abjurer gb chg gur 2 havg fuvcf.
– Qvggb vs lbh cynpr gur 4 havg fuvc va ebjf fvk guebhtu avar. Gurersber, vg zhfg tb va ebjf frira guebhtu gra.
– Similar logic will help you place the 3 unit ships, and the remainder will fall into place quickly after that.
– Last of all, svg gur svir fuvccvat ynarf vagb gur tevq. You’ll find that one of the givens wasn’t actually necessary!
I loved how this puzzle dispensed with some of the usual battleship procedures, such as worrying about adjacent ships, and turned the solving order on its head.
To clarify my trouble with the uniqueness logic I used (rot13) :
Gur ynarf arrq gb or onggyrfuvc / fhoznevar + pehvfre / fhoznevar + pehvfre / gjb qrfgeblref / qrfgeblre + gjb fhoznevarf gb znxr gbgnyf bs sbhe va rirel pbyhza.
Bapr V sbhaq gung gur onggyrfuvc pbhyq bayl or va pbyhza avar,
pbyhzaf guerr naq svir ybbx vqragvpny fb gurl zhfg obgu pbagnva gur fnzr fuvcf va beqre sbe gur chmmyr gb or havdhr, ob obgu pbyhzaf pbagnva n fhoznevar naq n pehvfre.
Nygubhtu guvf vf pbeerpg V qb abg yvxr gb hfr guvf xvaq bs ybtvp qhevat n fbyir.
Fb gur orggre ybtvp fubhyq or (nf Gevpvn fgngrq) gb qvfzvff ebjf fvk guebhtu avar sbe gur onggyrfuvc orpnhfr gur gjb qrfgeblref pnaabg or cynprq.
Gur onggyrfuvc va ebjf frira guebhtu gra yrnqf gb gjb fhof va ebj gra va pbyf guerr naq svir. Gur gjb qrfgeblref zhfg tb va pby frira. Fb gung yrnirf vaqrrq pbyf guerr naq svir vqragvpny jvgu n fhoznevar naq n pehvfre.
Ohg guvf gvzr V qvq abg hfr gur xabjyrqtr gung obgu pbyhzaf ZHFG or vqragvpny gb ernpu gur fbyhgvba.
23:52
I tried 6 places for the 4 unit battleship and went wrong 6 times before i placed it in the right place.Not a wednesday puzzle by any stretch of imagination.Could have easily been given as a saturday puzzle .Very difficult one.
I’m happy I came back to this puzzle! I think I used slightly different logic than the other solvers here:
V hfrq gur snpg gung gur obggbz gjb ebjf unq n 3 jvgu n 1 nobir gb pbapyhqr 2 fhof ba gur obggbz ebj. Fvzvyneyl e4 naq e2 unir gb unir gur bgure gjb fhof. Abj gur 3 frtzragf va e7 unir gb rnpu rkgraq rvgure hc be qbja 1, ohg abg obgu. ohg jr eha bhg bs qrfgeblref vs jr unir gurz nyy tb bayl bar havg, fb gur bar gung tbrf qbja 1 unf gb tb qbja 1 zber naq urapr or gur onggyrfuvc.
N yvggyr zber jbex jvgu fvzvyne ybtvp fubjf juvpu ebjf gur pehvfref unir gb or va, naq abj gurer’f rabhtu vasbezngvba gb trg nyy gur fuvcf cynprq.
can someone help me out with how to proceed in this puzzle ?
What is the trick to use ?
The columns split into 5 specific groups of ships (or in one case ship). Deciding if the battleship (4) goes in the top or bottom is the next step. Where can two cruisers (size 3) fit if the battleship is in rows 1-4?
Thanks got it 🙂