The review of PencilPress 500+ Sudoku Extreme Puzzles continues with bottom right, page 17. Along with that, we return with Sudokuwiki to Moito Road to Mastery III-4, for an alternative solution without a trial.
There is nothing extreme about PencilPress br 17. The value 4 is completely placed immediately, and the S box is filled before a plunging collapse leaves many effects in reserve, but never needed as causes. That counters any claim of being “extreme”.
Moving on to Moito III-47, the basic trace was described as routine in the original post, and a basic trace wasn’t given. You can read it by lifting the givens from this grid showing the naked triple and naked pair in line marking.
Before my party got started, Sudokuwiki uncovered two hidden unique rectangles I missed. The r45c37 rectangle is a Type 1, with two slinks from the corner opposite the bv. 2r5c3 cannot stay, because the removal of 3r5c3 both adjacent corners forces 3, making a reversible rectangle with a second solution. The r12c68 rectangle is a Type 2, slinked across two boxes. Figure out why 4r1c7 must go.
The hidden UR removals are indecisive, and were carried along in the original post.
My first finds, an XY-chain extended by a grouped 4-chain, and 9-chain ANL, boxline and naked triple it enables, were skipped by Sudokuwiki’s going directly to AIC building, with this AIC confirming ANL. Such a creature can be spotted by starting a boomerang from a bv cell.
Follow up marking
includes the naked triple at left.
Then the long XY ANL below triggers the collapse of Moito III-47, starting with:
The color trial is avoided.
Next post, it’s PencilPress Extreme 25, offering a challenging bypass.
Beginning also is an update on the collection of the review of an early “tells all”, which led me to the conclusion that tracing is a necessity.
In that first collection review, the full results for each review puzzle were not published. It soon became the Sysudoku custom to do that, so this update will follow suit for Sheldon’s Master Class. Here is the starting grid for Master Class 30.