The New Sudoku Players' Forum

[bikelarry718]

Don't know anything about x's quads or triples. I pencil in all possibilites.
I make an extra large grid using Excel, so I have a lot of room to pencil in possibilities. I start at the top left and start penciling in possibilities. Usually starting with 1 going to 9. I then search for single occurrences in rows, columns, and boxes. However, in the puzzle below, this procedure does not seem to work. Asking for suggestions as to other procedures.

l***l3**l*9*l
l*5*l***l*78l
l***l*18l3*2l
l4*5l*9*l***l
l**6l*8*l4**l
l***l*64l5*9l
l8*9l456l***l
l56*l***l*8*l
l*2*l8*1l9**l

My pencil marks indicate that in box 3,r1c7 and r2c7 the pencil marks 1 and 6 are noted. Don't know where to go from there. I've scrolled through the puzzle at least 6 times and only uncovered 4 answers. They are in bold.[/b]

[Nick67]

You are on the right track.

Don't know anything about x's quads or triples.

Suggestion: check out this web page for an excellent description of patterns to search for.

The next step is to scan each row (then each column, then each box)
for these patterns. When you recognize a pattern, you
can then often eliminate some candidates from cells related
to the cells in the pattern. (You mentioned you already use
this scanning procedure, but you've only been searching
for "singles". That's not enough, for many puzzles.)

Whenever you eliminate any candidate in any cell, you may
want to re-scan the cells in the same column, row, and box
as that cell, to see if you can find a pattern that wasn't there before.

You can do this with pencil and paper. However, using a program
makes it easier to search for some of the patterns.
For example, you might look here:

Simple Sudoku web page

[Nick67]

My pencil marks indicate that in box 3,r1c7 and r2c7 the pencil marks 1 and 6 are noted. Don't know where to go from there.

By the way, the pattern you have identifed is called a "naked pair",
and can be used to eliminate some candidates in c7.