The New Sudoku Players' Forum

[smolick]

Hi,

Im stuck. What should i do here? And how should i think?

Regards
Viktor

[urhegyi]

I tried myself from what I think was the start of the game:

Code: Select all

.6..1...9......7268.92...........5.2.7.5.8.3.5.8...........62.3634......7...8..9.

first step: R2C1 or R2C3 has to be 3 so R2C56<>3(R1C4 or R1C6 has to be 3 with the same elimination as result):pointing/claiming: R6C5=3(only possibility in column 5)
second step: Uniqueness type 1:R2C1=1/3;R4C13=1/3-->R2C3<>1/3=5!
stte

[Leren]

Using urhegyi's start position this is where I think the PM is.

Code: Select all

*-----------------------------------------*
| 2  6    7   | 34  1     35   | 8 45  9  |
|*13 145 *135 | 8   459-3 59-3 | 7 2   6  |
| 8  45   9   | 2   6     7    | 3 1   45 |
|-------------+----------------+----------|
| 13 9    13  | 6   7     4    | 5 8   2  |
| 4  7    6   | 5   2     8    | 9 3   1  |
| 5  2    8   | 139 39    139  | 4 6   7  |
|-------------+----------------+----------|
| 9  8    15  | 147 45    6    | 2 457 3  |
| 6  3    4   | 79  59    2    | 1 57  8  |
| 7  15   2   | 134 8     135  | 6 9   45 |
*-----------------------------------------*

A pointing pair of 3's in r2c13 removes 3 from r2c56 and gets you to here.

Code: Select all

*-----------------------------------------*
| 2  6   7   |b34  1   35  | 8 a45    9   |
| 13 145 135 | 8   459 59  | 7  2     6   |
| 8  45  9   | 2   6   7   | 3  1     5-4 |
|------------+-------------+--------------|
| 13 9   13  | 6   7   4   | 5  8     2   |
| 4  7   6   | 5   2   8   | 9  3     1   |
| 5  2   8   | 19  3   19  | 4  6     7   |
|------------+-------------+--------------|
| 9  8   15  | 147 45  6   | 2  57-4  3   |
| 6  3   4   | 79  59  2   | 1  57    8   |
| 7  15  2   |c134 8   135 | 6  9    d45  |
*-----------------------------------------*

A Skyscraper in cells a-b-c-d removes some 4's as shown. The puzzle solves with singles from there. You can see how Skyscrapers work here. Hodoku's solution was the same. Leren

[eleven]

The UR (equivalent to urhegi's) alone solves it, and it is easy to spot.

Code: Select all

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

The cells marked # in r2c1, r4c13 can only be 13. Since r2c3 must not be 13 then, at least one of 13 must be in the only free cells r23c2 in the boxes 1 and 4. Then r2c2 must be 1.