Advanced methods and approaches for solving Sudoku puzzles

Hi, fairly new to sudoku (havent failed yet, but this one has me foxed...)what techniques can i use to solve this puzzle (it's a super sudoku from the Times)

{3}{1}{59}{258}{4}{7}{89}{289}{6}
{59}{24}{6}{258}{3}{258}{1}{2489}{7}
{8}{7}{24}{6}{9}{1}{24}{5}{3}
{14}{5}{148}{48}{2}{3}{6}{7}{9}
{7}{248}{3}{9}{1}{6}{5}{24}{248}
{6}{9}{248}{7}{5}{48}{248}{3}{1}
{49}{3}{489}{1}{6}{249}{7}{2489}{5}
{1459}{46}{7}{245}{8}{2459}{3}{12469}{24}
{2}{468}{1459}{3}{7}{459}{49}{1469}{48}

would appreciate any advice and guidance
welshguy

Posts: 4
Joined: 12 October 2005

You have hidden pairs in box 7 and column 8. Once they're eliminated, the puzzle can be finished with singles alone.

If you haven't used hidden pairs before, I can show you how to find the pair in box 7. In this case you have the following candidates in that box:
Code: Select all
`49    .     4891459  46    ..     468   14589`

Notice the 1 can only go in two places. The 5 can only go in those same two places. Therefore, since one must be the 1 and one must be the 5, no other candidates will work there.
Code: Select all
`49    .     48915    46    ..     468   15`

Armed with that you should be able to find the one in column 8.
Lummox JR

Posts: 125
Joined: 22 September 2005

got it...thanks very much....sometimes you just need a good example to make things clear
welshguy

Posts: 4
Joined: 12 October 2005

ok, i see the hidden pair in box seven. the 1 and the 5 are unique, however in column 8 i have {248}{24}{48}.
With the 4 being common to all three candidates, there are no unique pairs. Am I looking at this the wrong way?
welshguy

Posts: 4
Joined: 12 October 2005

Without solving the puzzle myself, the example you just posted is a Naked Triple and works just the same way as a Naked/Hidden Pair, i.e. you can often exclude some candidates when you find one.
Karyobin

Posts: 396
Joined: 18 June 2005

The way you're looking at it is not wrong, although it is in the wrong column. That's a naked triple in column 9, but it won't do you much good because those are the only cells in that column that aren't already filled. Column 8 has six unfilled cells, and there is definitely a hidden pair there. You could also look in just box 9, because the pair can be found there as well.
Lummox JR

Posts: 125
Joined: 22 September 2005

now I have established the difference between columns 8 & 9 (don't you just feel an idiot sometimes?). Yes I can see what u mean...thanks again
welshguy

Posts: 4
Joined: 12 October 2005

I was wondering if I could get some help with spotting hidden pairs. I ask this because I actually found the naked quad in column 8 first (r1c8, r2c8, r5c8, and r7c8), instead of finding the hidden pair. It's true that this ended up eliminating the same candidates that the hidden pair would have, but it seems like finding a pair should be easier than finding a quad. Any tips on this subject?
Hanyou Hottie

Posts: 8
Joined: 15 October 2005

Yeah, they're two sides of the same coin, so there's always a hidden something and a naked something that together make up all the remaining cells in the row/col/box. Whichever you find, they do the same thing.
PaulIQ164

Posts: 533
Joined: 16 July 2005