## using paper and pencil

Advanced methods and approaches for solving Sudoku puzzles

### using paper and pencil

I find solving easy and medium puzzles on paper manageable enough, without too
much frustration. It puts me into some sort of extatic state of consciousness
when I feel it was hard but logic.

Anyway, here is my problem: I failed every single hard or very hard puzzles I
tried until now _ON_PAPER_. I manage to solve some hard and very hard puzzles
using the Simple Soduku program from Angus Johnson
(http://www.angusj.com/sudoku) but when trying on paper, when it comes to
writing down cell by cell all candidates, and then eliminate a part of them, I
find the step too tediuous and somehow, I always make mistakes.

Do you people use some special methods for organizing your "work" on paper? My
method is this:
(1) do the most I can using logic without writing candidates
in cell (I scan for "logical oportunities" now and then, even after writing
down the candidates numers in cells)
(2) write down the candidates into the cell (although I can never tell if I
overlooked something)
(3) try pair elimination (naked pairs, hidden pairs, etc), column/row/box
checking etc
(4) if everything else fail, search for x-wings, swordfishes etc.

Problems I encounter:
(a) for hard and very hard puzzles there are many candidates in a cell:
writing them all correctly is difficult
(b) when I want to inspect, let's say the 8-s, I find it difficult to isolate
them on paper
(c) each time I find the place of a number, I have to update the
row, the column and the box (source of error)

For those of you who can do hards and very hards on paper: how much time does it takes,
and when does it start to become boring?
In my case, if a puzzle takes more than one hour (OK, maybe two)
it's just too frustrating and the satisfaction goes away.

Maybe using Angus's Simple Soduku made me lazy, anyway, I think that solving
them on paper, with no aid, is the "right" way (at least for me).
I do not feel much satisfaction after solving a hard puzzle using the Simple Soduku
program. Maybe, it makes things just too easy to see.
mf625

Posts: 1
Joined: 28 June 2005

Personally, I use the Pappocom software when I'm trying to solve a puzzle as quickly as possible, but with a minimum of aids; I play with the Hall of Fame eligibility activated. I use the Simple Sudoku program when I want to try solving a very difficult puzzle as quickly as possible but with all the benefits of the filtering, colouring, and automatic pencilmarks. However, when I really want reach that "ecstatic state of consciousness" you mentioned, I play on paper; nothing beats good old paper (except scissors). (Edit: I use software when I want to play fast-and-furiously, hell-bent-for-leather: a computer program is much more forgiving if I happen to make a mistake.)

When playing on paper, mistakes are the worst thing that can happen. Unless caught immediately, it can often result in having to restart the puzzle. My best piece of advice: play slowly and double-check your work (which goes hand-in-hand with playing slowly). When you place a pencilmark, double-check for a big number that would "block" it (to clarify: look for the 6 at r3c1 before you try to place a pencilmark 6 at r7c1). Before placing a big number, verify that no other candidates remain for that cell. Once you place the big number, check twice that you remove all relevant pencilmarks.

When I'm playing on paper, if I know how difficult a puzzle is, it will affect how carefully I play. On paper, I never "play for speed" unless I know the puzzle is rated as easy. When playing a "very hard" on paper, it can stretch on for two or three days because I will usually only play for ten or fifteen minutes at a stretch. I find this also helps when trying to find elusive patterns because I keep coming back to the puzzle with a fresh set of eyes. I never tend to get bored because I will only stare at the puzzle for so long before putting it away until later. I will jot notes to keep track of what I have looked for: "searched 1's, 2's, 3's for x-wing". I admit that I will get frustrated if I haven't made progress for a long time but that makes the ah-ha moment even better when I finally crack the puzzle open.
scrose

Posts: 322
Joined: 31 May 2005

I have only ever solved puzzles with pen and paper, and making mistakes is just part of the game.

The best tips I can offer are:
1) Practice. The more you get used to just using paper the more instinct you develop for sensing you've just made a mistake (or even better you were just about to but didn't ).
2) Use a larger grid, not the tiny newspaper grids.
3) Expect to take more time.
4) Take a photocopy when you have completed the donkey-work (then you can always retreat to that point if you make an error).
5) Take a break when you've filled in the pencil marks (that bit always kills me, but when I restart its quite quick just to check for silly mistakes).

In spite of occasional tragedies, like finding out I'd made an error about 120 squares earlier on the Saturday samurai, I find the satisfaction of a successful full pen & paper grid makes up for this. To me its unimaginable to use the computer.
The very best feeling is when I complete a Fiendish or Very Hard on my pen&paper grid with zero pencil marks. It sure takes longer, but I also know very few achieve this.
little Zivvy

Posts: 7
Joined: 13 June 2005

I guess this is similar in some ways to the debate about T & E. There will be those who advocate a minimalist approach to pencil marks and those who write every possibility in every square and keep crossing out as they go along. Go with whatever floats your boat: it's supposed to be entertainment.

Personally, I only use pencil marks when I know a number must be in a particular row or column within a box. (I underscore the number to show it must be in that row.) In this way I find the puzzle doesn't become too cluttered, and that it's just about possible, even with the most fiendish of puzzles, to retain an overview of the progress I've made.

I seem to recall that an article in The Times implied men and women were likely to have different approaches to pencil marks. I don't know whether there's any real truth in that.

Incidentally, I find it extraordinarily difficult to resume a puzzle from which I've been broken off. Certainly the 'putting away until later' approach isn't one I benefit from. Is that just me?
demdempster

Posts: 8
Joined: 11 June 2005

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