The New Sudoku Players' Forum

[gilsud]

Hi All,
Has anyone done the USA July 12, 2015 Sudoku?
It has 5 stars for a difficulty rating and I often do them, but this time I've only completed the lower 3 blocks (except for r7 c4, and r7 c6, and those two cells are a matching pair of 5 and 9). I'm assuming that r means row and that c means column.
But other than the lower 3 rows, I only added 5 numbers.
I've only been doing Sudoku for about a month so I don't understand some techniques like x-wing and swordfish most of the time, but I find it odd to have basically completed the lower 3 rows and not much else. I've tried the puzzle twice and end up stumped at this same spot. I imagine that I'll need to read a Sudoku book before trying to complete it.
Best wishes, Gil.

[denis_berthier]

Has anyone done the USA July 12, 2015 Sudoku?
It has 5 stars for a difficulty rating ...

5....13..
.1..839..
..9.6..1.
3.....5..
.9..5..7.
..5.....1
.8..2.4..
..781..3.
..26....9

Apart from singles and whips[1] (= claiming, pointing) it requires only two hidden pairs:
whip[1]: c7n8{r6 .} ==> r4c9 ≠ 8
whip[1]: c7n6{r6 .} ==> r4c9 ≠ 6
hidden-pairs-in-a-row: r5{n1 n4}{c3 c4} ==> r5c4 ≠ 2, r5c3 ≠ 8, r5c3 ≠ 6
hidden-pairs-in-a-row: r4{n6 n8}{c3 c6} ==> r4c6 ≠ 9, r4c6 ≠ 2, r4c3 ≠ 4, r4c3 ≠ 1

[daj95376]

Code: Select all

5....13...1..839....9.6..1.3.....5...9..5..7...5.....1.8..2.4....781..3...26....9

 +-----------------------+
 | 5 . . | . . 1 | 3 . . |
 | . 1 . | . 8 3 | 9 . . |
 | . . 9 | . 6 . | . 1 . |
 |-------+-------+-------|
 | 3 . . | . . . | 5 . . |
 | . 9 . | . 5 . | . 7 . |
 | . . 5 | . . . | . . 1 |
 |-------+-------+-------|
 | . 8 . | . 2 . | 4 . . |
 | . . 7 | 8 1 . | . 3 . |
 | . . 2 | 6 . . | . . 9 |
 +-----------------------+


 after Singles
 *---------------------------------------------------------------------*
 | 5      247    468    | 2479   479    1      |  3      24     2468   |
 | 267    1      46     | 247    8      3      |  9      5      246    |
 | 28     3      9      | 245    6      25     |  7      1      248    |
 |----------------------+----------------------+-----------------------|
 | 3      247    1468   | 12479  479    2689   |  5      249    24-68  |
 | 268    9      1468   | 124    5      268    | *68     7      3      |
 | 2678   247    5      | 3      479    2689   | *68     249    1      |
 |----------------------+----------------------+-----------------------|
 | 1      8      3      | 59     2      59     |  4      6      7      |
 | 9      6      7      | 8      1      4      |  2      3      5      |
 | 4      5      2      | 6      3      7      |  1      8      9      |
 *---------------------------------------------------------------------*

   c7b6  Naked  Pair                     -68   r4c9     (*)


 *-----------------------------------------------------------------------*
 |  5     *247    68-4   | *2479  *479    1      |  3     *24     68-24  |
 |  267    1      46     |  247    8      3      |  9      5      246    |
 |  28     3      9      |  245    6      25     |  7      1      248    |
 |-----------------------+-----------------------+-----------------------|
 |  3     #247    68-14  |  12479 #479    68-29  |  5     #249   #24     |
 | %268    9      14-6   |  14-2   5     %268    | %68     7      3      |
 |  2678   247    5      |  3      479    2689   |  68     249    1      |
 |-----------------------+-----------------------+-----------------------|
 |  1      8      3      |  59     2      59     |  4      6      7      |
 |  9      6      7      |  8      1      4      |  2      3      5      |
 |  4      5      2      |  6      3      7      |  1      8      9      |
 *-----------------------------------------------------------------------*

 r1      Hidden Pair/Naked Quad          =68   r1c39     (*)
 r4      Hidden Pair/Naked Quad          =68   r4c36     (#)
 r5      Hidden Pair/Naked Triple        =14   r5c34     (%)


 Singles complete the puzzle


Solution:
576941328214783956839265714348176592691452873725398641183529467967814235452637189


_

[gilsud]

Thanks for the replies. I didn't realize my question was posted, there was a delay.

It's interesting that the reply daj95376 of 'where the singles finished' is exactly where I ended up each time.
I'll get a Sudoku book in the next month to figure out how to advance further, if possible for me. It will help me with definitions too, because I don't even know what 'singles', 'whips', 'naked and hidden pairs' refers too. There are probably many other definitions that I need to know too.

Thanks again for the replies, enjoy the summer, I may do some kayaking today, Gil.