Grinding Down Insane 495 with LPO Coloring

In this concluding post on Insane 495, one of two clusters is expanded by several means, including color LPO and a nice loop, merging clusters and reaching a point where an easy trial color wraps it up.  Insane 495 is  a review puzzle from  A review of this collection is concluding, with basic solving of the last review puzzle, Insane v.4 b.10 n.5 being checkpointed in this post.

IN 495 finned 5-wingI hope you found the productive finned 5-wing and noticed the shortcut forcing chains by which victims see the fin. It’s classic sysudoku.

The cluster extension to an orange 5-candidate in r7c3 traps two, including the fin.




IN 495  nicely colored loopNext, a tightly wound,  bv generated nice loop extends the red/orange cluster, trapping four. Two of its nodes were already colored, identifying the nice loop colors as red and orange. It’s good to be aware of that possibility.

Row r2 suggests that orange is blue, but it could be that green and red are true.



IN 495 3 freeformsSeeing that the two clusters share 3’s, I call on the pink olive 3-patterns of the last post:

Matching colors, the single olive pattern is green, and the pink candidates eligible for coloring are blue. It’s enough to merge green into red and blue into orange.



IN 495 ANLThe merge traps 2 in r2c1, enabling the  ANL removal, and 3 in r6c1. When 3 in r1c2 becomes orange, the 3 in r1c6 is trapped, and the N3 clue is born.


These 3-candidates leaving the grid, we are down to two 3-patterns,  the red 3e and the orange 3c.

IN 495  orange on trialFrom the conflict tables of the last post,  I recall that 3c => 7a, so I can add color 7a orange, and 7b red.  Traps bring in more bv.  It’s double solution or a quick contradiction of red or orange.  I put orange on trial.

Orange forces two 5-candidates into r4. The red removals generate two 28 naked pairs. One promotes a 4 that promotes one 5. The other starts a 9-chain that confirms the other 5.

I will leave the trial trace that makes this evident up to you, claiming credit for genius Sudoku vision that I never will have.  The red candidates dictate a solution forthwith.


About Sudent

My real name is John Welch. I'm a happily married, retired professor (computer engineering), timeshare traveling, marathon running father of 3 wonderful daughters and granddad to 7 fabulous grandchildren. The blog is about Sudoku solving. It covers how to start, basic solving to find candidates efficiently, and advanced solving methods in an efficient order of battle. It is about human solving methods, not computer solving.
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