tarek wrote:There was a hidden triple in the same row as the naked double, (247) in r2c469......

You saw the naked double before that hidden triple, what do you think of that !!!

Would you say that spotting naked doubles is easier than hidden triples on the non PM grid?

It very much depends. Inside a box I spot the hidden triplets very easily, definately before a naked double as I can do it by "drawing lines":

- Code: Select all
`...|...|.12`

.5.|.46|7..

...|...|..3

or

...|..2|... ...|..2|...

...|...|... ...|...|...

...|...|... ...|...|...

---+---+--- ---+---+---

...|..7|... ...|...|...

1..|5.6|.23 1..|...|.23

...|4..|... ...|4..|...

---+---+--- ---+---+---

...|...|... ...|...|...

...|..1|... ...|..1|...

...|..3|... ...|..3|...

[edit: note that the hidden triplet is actually easier to see when it's got a naked quintuplet counterpart, not any extra information "blocking your vision"]

In rows and columns I search in a different way, even for hidden singles. I mentioned in the original post how I count through the row and find the missing numbers, then I compare each cell to this set of numbers. In row 2 of your example I found that the missing numbers were 12478, then I compared each cell, c3 could see 247, c4-17, c6-1, c8-247. Then I didn't need to check the last cell, I knew that if two cells can see three out of five missing numbers, there must be a naked pair. Then I rechecked the remaining cells (c469) against the remaining three numbers only (to find possible singles). When I do it like this I think there isn't any difference if the set is naked or hidden, I'll find it anyway .

This is of course only how I do it, other people may experience it in another way, but the order I spot things is something like:

-Hidden singles within boxes

-Locked candidates

-Hidden pairs/triplets within boxes

-UR

-naked singles

-subsets in rows/columns

I usually don't look for x-wings before I scanned all of the above, I think the puzzle you posted would have required a lot more time if you hadn't mentioned the x-wing.

RW