The New Sudoku Players' Forum

[jvs]

I'm stuck on a "superior" puzzle, the most advanced level, by Wayne Gould in his book Grand Master Su Doku. Here is the initial puzzle and following that is my solution so far with pencil marks. I would greatly appreciate a hint and a pointer to the technique to use for the next step.

Code: Select all

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

9      2368  38  | 7   4    5 | 26  236    1
1258 123568   7  | 9 168   68 | 4  2356   35
15      156   4  | 3  16    2 | 8     7    9
-----------------+------------+--------------
3       478  58  | 1   9  478 | 56  468    2
2458  24578   1  | 6  78 3478 | 9  3458 3458
6        48   9  | 2   5  348 | 1   348    7
-----------------+------------+--------------
45       39   6  | 8  23    1 | 7    29   45
148    1489   2  | 5  67   67 | 3  1489   48
7       138 358  | 4  23    9 | 25  128    6



[sweetbix]

In box 2 the 8s must be in row 2 therefore they cannot be in row 2 in box 1 & 3. This leaves you with only two 8s in c19 and both are in r58. This is an Xwing and allows you to remove all the other 8s across rows 5 and 8.

[jvs]