Sudoku Players' Forum (clone)

Hello again.

Am I just blind or is this puzzle harder than it looks like ?

Why would you say that this puzzle looks easy? The number of clues present is a very bad indicator of puzzle complexity.

This puzzle is noticeably more difficult than any you have posted so far.

Code: Select all

*--------------------------------------------------------------*
| 6     13    7      | 8     5     2      | 9     4     13     |
| 4     2     9      | 1     7     3      | 5     8     6      |
| 13    5     8      | 6     9     4      | 2     7     13     |
|--------------------+--------------------+--------------------|
| 5-8   7     6      | 3     2    d18     | 4     15    9      |
| 9     38    1      | 5     4     68     | 7     36    2      |
| 35    4     2      | 9     16    7      | 136   1356  8      |
|--------------------+--------------------+--------------------|
| 2    b16    5      | 7     3    c16     | 8     9     4      |
| 7     168   4      | 2     168   9      | 136   136   5      |
|a18    9     3      | 4     168   5      | 16    2     7      |
*--------------------------------------------------------------*

A move that solves this puzzle is called a W Wing. The chain for this one is written (8=1) r9c9 - r7c2 = r7c6 - (1=8) r4c6 => - 8 r4c1

This chain shows that at least one of r9c9 or r4c6 must be 8. Since r4c1 sees both of these cells it can't be 8. The puzzle then solves easily.

For W Wings look for a pair of bi-value cells with the same 2 digits - the elimination digit (8 here) and the non-elimination digit (1 here).

The W Wing occurs when there is a Strong link in the non-elimination digit between 2 cells that can see the bi-value cells (ie 2 1's in Row 7 here).

Leren

Hi Leren. This is very nice approach again, thank you