Cobra Roll

Post puzzles for others to solve here.

Cobra Roll

hello all! this puzzle is one i've spent the last few days working on. i'm quite happy with it!
Code: Select all
`.-------.-------.-------.| . . 2 | 3 . . | 5 . . || . 1 . | . 4 . | . 9 . || . . . | 5 . . | . . 6 |+-------+-------+-------+| . 7 6 | . . . | . . . || 8 . . | . 2 . | . 4 . || 9 . . | . . . | 8 . 3 |+-------+-------+-------+| . . . | . . 5 | . . 2 || . . . | . . 6 | . 1 . || . . . | 8 7 . | . . . |'-------'-------'-------'`

very interested to see your solutions!
Last edited by jovi_al01 on Wed Aug 18, 2021 12:38 am, edited 1 time in total.

jovi_al01

Posts: 66
Joined: 26 July 2021

Re: Cobra Roll

this one is an absolute gem to me! very familiar patterns

Code: Select all
`.---------------------------.----------------------.--------------------.| 467      4689     2       | 3      1689   1789   | 5      78    14    || 3567     1        3578    | 267    4      278    | 23     9     78    || 347      3489     34789   | 5      189    12789  | 14     23    6     |:---------------------------+----------------------+--------------------:|#1234-5   7        6       |*149   *13589 #34-189 | 129    25    159   || 8        35       135     | 1679   2     *1379   | 1679   4     1579  || 9        245      145     | 167-4  156   *147    | 8      2567  3     |:---------------------------+----------------------+--------------------:|*13467    34689    34789-1 | 149    139    5      | 34679  3678  2     ||*23457    34589-2  345789  | 249    39     6      | 3479   1     45789 ||#12-3456 *234569  *13459   | 8      7     #1234-9 | 3469   356   459   |'---------------------------'----------------------'--------------------'`

8 Truths = {34R4 12R9 12C1 34C6}
8 Links = {49n1 49n6 34b5 12b7}
-189r4c6 -3456r9c1 -1r7c3 -2r8c2 -4r6c4 -5r4c1 -9r9c6
stte

decided to use xsudo for this one, slowly learning how to work with it ヽ(´▽`)/

shye

Posts: 158
Joined: 12 June 2021

Re: Cobra Roll

that's my solution too, shye! (i think-- i don't understand the notation all that well, but it looks like you got the same eliminations i did )
this one was inspired by some of your recent work! thanks for being a wonderful muse and thank you for the kind words!

jovi_al01

Posts: 66
Joined: 26 July 2021

Re: Cobra Roll

a less intimidating looking solution, which does the same thing:

at least one of r4c1, r9c1 & r9c6 must be a 1 (else repeat 1 in b7)
at least one of r4c1, r9c1 & r9c6 must be a 2 (else repeat 2 in b7)
at least one of r4c1, r4c6 & r9c6 must be a 3 (else repeat 3 in b5)
at least one of r4c1, r4c6 & r9c6 must be a 4 (you get the picture)
4 cells for 4 candidates, all others removed

shye

Posts: 158
Joined: 12 June 2021

Re: Cobra Roll

jovi_al01 wrote:this puzzle is one i've spent the last few days working on. i'm quite happy with it!

Thanks for sharing !

shye wrote:a less intimidating looking solution, which does the same thing:

at least one of r4c1, r9c1 & r9c6 must be a 1 (else repeat 1 in b7)
at least one of r4c1, r9c1 & r9c6 must be a 2 (else repeat 2 in b7)
at least one of r4c1, r4c6 & r9c6 must be a 3 (else repeat 3 in b5)
at least one of r4c1, r4c6 & r9c6 must be a 4 (you get the picture)
4 cells for 4 candidates, all others removed

Awsome !

Here is a "classical" solution in four steps (much less attractive )
Code: Select all
` +-----------------------------+-------------------------+-------------------------+ |  467      4689     2        |  3    Dd1689    1789    |  5       78     14      |  |Bb56-73    1      Ab35-78    |Cc267    4       278     | a23      9      78      |  |  347      3489     34789    |  5      189     12789   |  14     g23     6       |  +-----------------------------+-------------------------+-------------------------+ | F1234-5   7        6        |  149  Ef13589  E13489   |  129    g25     19-5    |  |  8       G35       13-5     |  1679   2       1379    |  1679    4      1579    |  |  9        245      145      |  1467 Ee56-1    147     |  8       567-2  3       |  +-----------------------------+-------------------------+-------------------------+ |  13467    34689    134789   |  149    139     5       |  34679   3678   2       |  |  23457    234589   345789   |  249    39      6       |  3479    1      45789   |  |  123456   234569   13459    |  8      7       12349   |  3469    356    459     |  +-----------------------------+-------------------------+-------------------------+`

1. (3)r2c7 = (35-6)r2c13 = r2c4 - r1c5 = (6-5)r6c5 = r4c5 - (5=23)r34c8 loop => -7 r2c13, -8r2c3, -1 r6c5, -5 r4c19, -2 r6c8
2. (5)r2c3 = (5-*6)r2c1 = r2c4 - r1c5 = (658-3)b5p238 = r4c1* - (3=5)r5c2 => -5 r5c3, -3r2c1*

Code: Select all
` +------------------------------+-------------------------+-------------------------+ |    467      4689    2        |  3      1689    1789    |  5       78     14      |  |    56       1       5-3      |  267    4       278     | f23      9      78      |  |    347      3489    34789    |  5      189     12789   |  14      23     6       |  +------------------------------+-------------------------+-------------------------+ |   E134      7       6        |De149    13589 Cd13489   | e129     25   De19      |  |    8        35    Fa13       |  1679   2       1379    |  1679    4      1579    |  |    9        2      F145      |  1467   56    Cd147     |  8       567    3       |  +------------------------------+-------------------------+-------------------------+ |    13467    34689   134789   |  149    139     5       |  34679   3678   2       |  |    23457    34589   345789   |  249    39      6       |  3479    1      45789   |  | HAc12346-5  34569 Gb13459    |  8      7    HBc12349   |  3469    356    459     |  +------------------------------+-------------------------+-------------------------+`

3. (3=1)r5c3-r9c3=(12-4)r9c16=r46c6-(4=192)r4c479-(2=3)r2c7 =>-3r2c3
4. (2)r9c1=(2-4)r9c6=r46c6-(4=91)r4c49-r4c1=r56c3-r9c3=(12)r9c16 =>-5r9c1; ste
Cenoman
Cenoman

Posts: 1873
Joined: 21 November 2016
Location: Paris, France

Re: Cobra Roll

Great solution !

Here is a complex alternative:
Note the ALS's 12349 in r78c45 (#) and 1259 in r4c789 (@).
Code: Select all
` *---------------------------------------------------------------------------------* |  467      4689     2        |  3      1689    1789    |  5       78     14      | |  3567     1        3578     |  267    4       278     |  23      9      78      | |  347      3489     34789    |  5      189     12789   |  14      23     6       | |-----------------------------+-------------------------+-------------------------| | B1234-5   7        6        | A149    8-1359  348-19  | @129    @25    @159     | |  8        35       135      |  1679   2       1379    |  1679    4      1579    | |  9        245      145      |  167-4  156     147     |  8       2567   3       | |-----------------------------+-------------------------+-------------------------| | x13467    34689    134789   | #149   #139     5       |  34679   3678   2       | | y23457    234589   345789   | #249   #39      6       |  3479    1      45789   | | *123456   234569   13459    |  8      7       1249-3  |  3469    356    459     | *---------------------------------------------------------------------------------*`

If 4 in #, then (19 in r4c4) 1259 in r4c4789 and 12 (not in r5c1) in r789c1: one of them missing in # -> 3r78c5
If 4 not in #, but 1239 => (hidden pair) 12r59c1 -> 1259 in r4c1789 and 3r78c5, 4r4c4
=> -1359r4c5, -19r4c6, -5r5c1, -4r6c4, -3r9c6; stte

[Edit:] Cenoman pointed out, that these elimantions are not enough for ste or bte, thanks.

However this can be repaired:
In the first case 12 are in r789c1, and not both can be in r78c1 (leaving only 3 digits in #), so we get 12r9c1
In the second case we have the hidden pair 12r59c1.
So also 3456r9c1 can be eliminated.

So we have
- 4r78c4, 1259 r4c4789, 3r78c5, 12r9c1 or
- 12r59c1, 1259 r4c1789, 4r4c4, 3r78c5
Last edited by eleven on Fri Aug 20, 2021 8:11 pm, edited 1 time in total.
eleven

Posts: 2788
Joined: 10 February 2008

Re: Cobra Roll

beautiful solution as well! thank you for spending time on this )

jovi_al01

Posts: 66
Joined: 26 July 2021

Re: Cobra Roll

.
SER = 8.5
Code: Select all
`Resolution state after Singles and whips[1]:   +----------------------+----------------------+----------------------+    ! 467    4689   2      ! 3      1689   1789   ! 5      78     1478   !    ! 3567   1      3578   ! 267    4      278    ! 237    9      78     !    ! 347    3489   34789  ! 5      189    12789  ! 12347  2378   6      !    +----------------------+----------------------+----------------------+    ! 12345  7      6      ! 149    13589  13489  ! 129    25     159    !    ! 8      35     135    ! 1679   2      1379   ! 1679   4      1579   !    ! 9      245    145    ! 1467   156    147    ! 8      2567   3      !    +----------------------+----------------------+----------------------+    ! 13467  34689  134789 ! 149    139    5      ! 34679  3678   2      !    ! 23457  234589 345789 ! 249    39     6      ! 3479   1      45789  !    ! 123456 234569 13459  ! 8      7      12349  ! 3469   356    459    !    +----------------------+----------------------+----------------------+`

1) simplest-first solution, in S+W6: Show
naked-pairs-in-a-block: b3{r1c8 r2c9}{n7 n8} ==> r3c8≠8, r3c8≠7, r3c7≠7, r2c7≠7, r1c9≠8, r1c9≠7
naked-pairs-in-a-block: b3{r2c7 r3c8}{n2 n3} ==> r3c7≠3, r3c7≠2
finned-swordfish-in-columns: n2{c7 c4 c1}{r4 r2 r8} ==> r8c2≠2
biv-chain[3]: r6n2{c2 c8} - r4c8{n2 n5} - b5n5{r4c5 r6c5} ==> r6c2≠5
z-chain[3]: c4n7{r6 r2} - b3n7{r2c9 r1c8} - r6n7{c8 .} ==> r5c6≠7
t-whip[4]: c5n5{r6 r4} - r4n8{c5 c6} - r4n3{c6 c1} - r5c2{n3 .} ==> r6c3≠5
t-whip[5]: r2n6{c1 c4} - c5n6{r1 r6} - c5n5{r6 r4} - r4n8{c5 c6} - r4n3{c6 .} ==> r2c1≠3
biv-chain[4]: r4c8{n5 n2} - b3n2{r3c8 r2c7} - r2n3{c7 c3} - b1n5{r2c3 r2c1} ==> r4c1≠5
whip[1]: b4n5{r5c3 .} ==> r5c9≠5
whip[5]: r4n8{c5 c6} - b5n3{r4c6 r5c6} - r5c2{n3 n5} - r5c3{n5 n1} - b6n1{r5c7 .} ==> r4c5≠1
whip[5]: r4n8{c6 c5} - b5n3{r4c5 r5c6} - r5c2{n3 n5} - r5c3{n5 n1} - b6n1{r5c7 .} ==> r4c6≠1
biv-chain[6]: r3c8{n2 n3} - r2n3{c7 c3} - b1n5{r2c3 r2c1} - r2n6{c1 c4} - c5n6{r1 r6} - r6n5{c5 c8} ==> r6c8≠2
hidden-single-in-a-row ==> r6c2=2
biv-chain[3]: c1n2{r9 r8} - c4n2{r8 r2} - r2n6{c4 c1} ==> r9c1≠6
t-whip[4]: c1n2{r9 r8} - c4n2{r8 r2} - r2n6{c4 c1} - c1n5{r2 .} ==> r9c1≠4, r9c1≠3, r9c1≠1
finned-x-wing-in-rows: n1{r9 r6}{c3 c6} ==> r5c6≠1
z-chain[3]: r6c3{n4 n1} - r9n1{c3 c6} - c6n4{r9 .} ==> r6c4≠4
t-whip[4]: r5c6{n9 n3} - r4n3{c6 c1} - c1n1{r4 r7} - b8n1{r7c4 .} ==> r9c6≠9
t-whip[4]: r6c3{n4 n1} - r9n1{c3 c6} - b8n2{r9c6 r8c4} - b8n4{r8c4 .} ==> r7c3≠4
z-chain[5]: r5c6{n9 n3} - r4n3{c6 c1} - c1n1{r4 r7} - r7c5{n1 n3} - r8c5{n3 .} ==> r4c5≠9
z-chain[5]: r9n1{c6 c3} - r6c3{n1 n4} - c6n4{r6 r4} - r4n8{c6 c5} - c5n3{r4 .} ==> r9c6≠3
whip[1]: c6n3{r5 .} ==> r4c5≠3
z-chain[5]: c5n5{r6 r4} - r4n8{c5 c6} - r4n3{c6 c1} - c1n1{r4 r7} - c4n1{r7 .} ==> r6c5≠1
t-whip[5]: b8n2{r8c4 r9c6} - r9n1{c6 c3} - b4n1{r5c3 r4c1} - r4n3{c1 c6} - r4n4{c6 .} ==> r8c4≠4
t-whip[5]: r4n3{c6 c1} - c1n1{r4 r7} - b8n1{r7c4 r9c6} - b8n4{r9c6 r7c4} - r4n4{c4 .} ==> r4c6≠9, r4c6≠8
singles ==> r4c5=8, r6c5=5, r1c5=6, r2c1=6, r2c3=5, r2c7=3, r3c8=2, r4c8=5, r4c7=2, r5c2=5
hidden-pairs-in-a-block: b7{n2 n5}{r8c1 r9c1} ==> r8c1≠7, r8c1≠4, r8c1≠3
finned-swordfish-in-columns: n1{c5 c7 c1}{r7 r3 r5} ==> r5c3≠1
stte

2) 3-step solution in W8, using my recent fewer steps algorithm (http://forum.enjoysudoku.com/reducing-the-number-of-steps-t39234.html)
This is the first solution it finds [the next 2 solutions in W8 were also 3-step, and I stopped it there]
=====> STEP #1
whip[8]: r4n8{c5 c6} - r4n3{c6 c1} - r4n4{c1 c4} - c6n4{r6 r9} - b8n2{r9c6 r8c4} - c1n2{r8 r9} - r9n1{c1 c3} - b4n1{r5c3 .} ==> r4c5≠5
singles ==> r6c5=5, r1c5=6, r2c1=6, r2c3=5,> r2c7=3
whip[1]: b3n2{r3c8 .} ==> r3c6≠2
=====> STEP #2
hidden-pairs-in-a-block: b3{n1 n4}{r1c9 r3c7} ==> r3c7≠2, r3c7≠7, r1c9≠8, r1c9≠7
singles ==> r3c8=2, r4c8=5, r5c2=5, r4c7=2, r6c2=2
=====> STEP #3
biv-chain[5]: b3n7{r1c8 r2c9} - r2c4{n7 n2} - r8n2{c4 c1} - r8n5{c1 c9} - b9n8{r8c9 r7c8} ==> r7c8≠7, r1c8≠8
stte
denis_berthier
2010 Supporter

Posts: 3176
Joined: 19 June 2007
Location: Paris

Re: Cobra Roll

I found a solution in 3 (non-basic) steps.
It took me a long time to find step 2 (looking carefully at eleven's solution helped).

After basics

Code: Select all
`.------------------------------------------------------------------------.| 467     4689    2      |  3     d1689    1789  |  5       78     14    || 3567    1       3578   | e267    4      e278   | f23      9     e78    || 347     3489    34789  |  5      189     12789 |  14      23     6     ||------------------------+-----------------------+-----------------------|| 1345-2  7       6      |  149   b13589   13489 | g129    a25     159   || 8       35      135    |  1679   2       1379  |  1679    4      1579  || 9       245     145    |  1467  c156     147   |  8       567-2  3     ||------------------------+-----------------------+-----------------------|| 13467   34689   134789 |  149    139     5     |  34679   3678   2     || 23457   234589  345789 |  249    39      6     |  3479    1      45789 || 123456  234569  13459  |  8      7       12349 |  3469    356    459   |'------------------------------------------------------------------------'`
1. (2=5)r4c8 - r4c5 = (5-6)r6c5 = r1c5 - r12c1 = (65-3)r2c13 = (3-2)r2c7 = r4c7 => -2 r4c1, r6c8 [1 placement]

Code: Select all
`.--------------------------------------------------------------------------.|  467      4689    2      |  3    la189+6   1789  |  5       78     14    ||  3567     1       3578   |  267    4       278   |  23      9      78    ||  347      3489    34789  |  5      189     12789 |  14      23     6     ||--------------------------+-----------------------+-----------------------|| j1345     7       6      | e149  jc13589  j13489 | d129    d25    d159   ||  8        35     i135    |  1679   2       1379  |  1679    4      1579  ||  9        2      i145    |  1467 kb156     147   |  8       567    3     ||--------------------------+-----------------------+-----------------------||  13467    34689   134789 | f149    139     5     |  34679   3678   2     ||  23457    34589   345789 | f249    39      6     |  3479    1      45789 || g123456   34569  h13459  |  8      7      g12349 |  3469    356    459   |'--------------------------------------------------------------------------'`

2. (6)r1c5=(6-5)r6c5=r4c5-(5=219)r4c789-(1|9=4)r4c4-(4)r78c4=(42-1)r9c16=r9c3-r56c3=(138-5)r4c156=(5-6)r6c5=(6)r1c5
=> +6 r1c5 [9 placements and eliminations by HP(25)r89c1]

Code: Select all
`.------------------------------------------------------------------.|  47    489    2      |  3     6     1789  | 5     a7-8     14    ||  6     1      5      | c27    4     278   | 3      9      b78    ||  347   3489   34789  |  5     189   1789  | 14     2       6     ||----------------------+--------------------+----------------------||  134   7      6      |  149   1389  13489 | 2      5       19    ||  8     5      13     |  1679  2     1379  | 1679   4       179   ||  9     2      14     |  1467  5     147   | 8      67      3     ||----------------------+--------------------+----------------------||  1347  34689  134789 |  149   139   5     | 4679  g368-7   2     || e25    3489   34789  | d249   39    6     | 479    1      f45789 ||  25    3469   1349   |  8     7     12349 | 469    36      459   |'------------------------------------------------------------------'`

3. (7)r1c8 = r2c9 - (7=2)r2c4 - r8c4 = (2-5) r8c1 = (5-8) r8c9 = (8) r7c8 => -7 r7c8, -8 r1c8; ste

Edit: insert explicit mention to my numbering of moves.
Last edited by jco on Fri Aug 20, 2021 12:29 pm, edited 1 time in total.
JCO
jco

Posts: 363
Joined: 09 June 2020

Re: Cobra Roll

jco wrote:I found a solution in 3 steps.
It took me a long time to find step 2 (looking carefully at eleven's solution helped).
After basics
Code: Select all
`.------------------------------------------------------------------------.| 467     4689    2      |  3     d1689    1789  |  5       78     14    || 3567    1       3578   | e267    4      e278   | f23      9     e78    || 347     3489    34789  |  5      189     12789 |  14      23     6     ||------------------------+-----------------------+-----------------------|| 1345-2  7       6      |  149   b13589   13489 | g129    a25     159   || 8       35      135    |  1679   2       1379  |  1679    4      1579  || 9       245     145    |  1467  c156     147   |  8       567-2  3     ||------------------------+-----------------------+-----------------------|| 13467   34689   134789 |  149    139     5     |  34679   3678   2     || 23457   234589  345789 |  249    39      6     |  3479    1      45789 || 123456  234569  13459  |  8      7       12349 |  3469    356    459   |'------------------------------------------------------------------------'`

Well, not really 3 steps, as two pairs eliminate 6 candidates before the start and you have one more HP after step 2.
So, in my view, that makes 6 steps - including one of length 17.
denis_berthier
2010 Supporter

Posts: 3176
Joined: 19 June 2007
Location: Paris

Re: Cobra Roll

simon did this puzzle on Cracking The Cryptic!