Hacker Puzzle!

This will make sense to people who look for answers !

7 for Uranus , 8th Planet Neptune
8 for Acht, neun for 9 in German
9 for Sept, Oct , the short form for the 10th month
10 for 10 of Spades, the Jack comes next
11 for eLeVeN, tWeLvE for 12
12 x 12 = 144, 13 x 13 = 169
13 for Number13, Number14 for 14
14 is Catorce, quince is 15 in Spanish
15th President of the Us is buchunan, 16th is Lincoln
16 is sedicim, septendecim is 17 in Latin
17 is 10001, 10010 is Binary 18 (old old code)
18 is argon, potassium the next in the periodic table
19 is ojofuffo minus one alphabet to each letter, and twenty minus one you get uxfouz
20 is icosagon - 20 side pentagon, 21 side is icosihenagon
21 is 10946 is a Fibonacci number, and the next is 17711
22 is very simple Vooey, and 23 must be Woody
23 is one crazy grandmother dancing to this long long night.

Puzzle Makers

Here you will find a partial list of other wooden jigsaw puzzle makers sites. By no means is it complete. If you make jigsaw puzzles and are not listed here, send me a link to your site and a short description of you and your company and I will be glad to add it. Once listed, I would appreciate it if you would reciprocate by adding www.bradypuzzles.com to your site.
Stave Puzzles MGC's Custom Made Wooden Jigsaw Puzzles Custom Puzzle Craft Jardin Puzzles Elms Puzzles Thingamajigsaw Puzzles J.C.Ayer & Company Dougs Puzzles KidPuzzles Jack in the Box Puzzles Positivelypuzzled.com

मथ्मेतिकल puzzle

Big Numbers
Boys and Girls
Charlie's Chickens
Rowing Across the River
Sneaking Spider
Beer and Bitterballs
Speedy Sums
Traveling Bird
Cork in the Canal
Square And Rectangle
Three Taps
Notable Number
Baffling Birthdays
William's Whereabouts
The Prince and the Pearls
Plus & Minus
Missing Pages
Postman Pat
All Apples
Camel & Bananas
Buying Books
Four Flies
Fabulous Fraction
Circling Cyclist
Odd Oranges
Water Bucket
The Cucumber Case
Palindrome Puzzle
Escalator Exercise
The puzzles are marked with stars () that show the degree of difficulty of the given puzzle.

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Sudoku Susser - free Sudoku solver / assistantMac/Windows/Linux; can solve any sudoku deductively; designed to help you improve your skill

play-sudoku.de! free and unlimited3 different levels! International Championship! Save your unsolved puzzles to continue later!

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InfoSudoku.com - FREE SUDOKU ONLINESpecialized sudoku website. Free Sudoku Play Online, 3 difficulty levels ,

Play Free Online Very nice sudoku site to play free online

www.sudokuportal.com Free Samurai Sudokus - Killer Sudokus - Online Sudokus - Printable Sudokus - Books - Shirts - Forums

Sudokuhints.comSudokuhints free online sudoku solver with daily graded difficulty puzzles with hints, bookmarking.

Su Doku Mania!Getting started with Su Doku? Download a free solver and free programs for Mac, Palm and PC.

Jumbo Sudoku SolverWe have 30 or more Sudoku programs. (Killer, Samurai, etc.)

Play Sudoku with 3000 free Sudokus in ExcelPlay Sudokus (2x2) (3x3)(4x4), also with Wordokupuzzles.Sudoku is fun and addictive!

THE FIRST SuDoKu GROUP IN THE NETHERE, YOU WILL FIND LOTS OF PEOPLE WILLING TO COMMUNICATE ABOUT SuDoKu

Daily free Sudokus with solutions in 4 levels.Daily free sudokus: Numbers, letters and colors...and growing up. Sudokus, Alfadokus and Colordokus.

Sudoku LinksOnly the best sudoku sites

Online Sudoku Solver and Generator.Easy to use, works with Windows, Mac, Linux.

Free downloadable Sudoku booksFree booklets of computer-graded puzzles in adobe PDF format. Regular, Samurai, Diamond & Hex!

Print or Play Sudoku 9X9,16X16,25X25 & Puzzles.Free Play Sudoku, Print 6 per page, Solver, Daily + Other Games + Puzzles

Download Sudoku XP for your PC!Download a free demo of Sudoku XP for the ultimate Sudoku experience!

Diagonal, Even-Odd and Classic from 4x4 to 12x12Assorted Sudoku puzzles to play online or print, weekly new and free. [Vinckensteiner]

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FREE SUDOKUPlay an infinity of Sudoku/Samurai; Solve any of them; Free download a great game, and its code!

Sudoku 9981Sudoku puzzle game for Windows

Sudoku AssistantA Java Applet that assists you in solving existing puzzles!

Michael Mepham's sudoku support siteThe Daily Telegraph, Los Angeles Times, Life Magazine & 100s of papers carry Michael Mepham's sudoku

NEW Sudoku PRIZE Competition !FREE PRIZE competition. Puzzles every week. PLUS software to solve & create puzzles.

SudokuMeister - create & play Sudoku puzzles (PC)SudokuMeister - create & play Sudoku puzzles on your PC. Free daily puzzle and trial download!

Everything there is to know about SudokuEvery single type of Sudoku featured (eg samurai) plus tactics compared from different sites.

The Definitive Sudoku HelperYou supply the logic, the helper does the fiddly bits

Top Notch SudokuFree gattai-5 ("samurai"), gattai-2 and wordoku puzzles. Weekly updates, prize puzzles and solvers.

Solver / Generator and Hints and TechniquesSadMan Software Sudoku

sudoku

link
Sudoku HollandGoogle NL lists it as the top sudoku site for Holland.
Sudoku SusserRobert has created one of the best solvers on the web. Extremely knowledgeable in the techniques of solving sudoku he has incorporated his strategies into this program for Windows or the Mac.
The Daily SudokuA new graded and printable Sudoku puzzle every day for free on a well-established website by a sudoku author and enthusiast
WikipediaVery good description of what sudoku is all about, its origins how to play and loads of links.
Nick JordanAnother enthusiast's FAQ
NikoliWhere it all really started: this is the website of the Japanese publisher that tidied up sudoku and made it what it is today. Site offers sudoku samples and help.
Picture SudokuThis is a unique form of Sudoku where people can 'unravel' a picture whilst solving the puzzle.
Remote Pairs - A Particular Case of XY-ChainsA formal paper on the relationship between Remote Pairs and XY-Chains
Su-DokuAn attractive daily sudoku site. Good graphics from Inertia Software.
Sudoku Funan online puzzle with a speed challenge
Sudoku Solver... By Logicexactly what it says on the tin
Sudoku HelperFree-on-line Helper, not solver, big grid, big numbers
Telegraph Crossword SocietyPay-to-play site that features most of the Daily Telegraph's crosswords and puzzles. Subscription gets you access to online puzzles and features.
Top 50 Kakuro Sites
Sudoku - the holiday companionIt's the book to make a plane journey last half the time and to keep you occupied during your quiet moments on the beach. The Daily Telegraph Sudoku is packed with 132 new puzzles compiled by Mike Mepham. Orders for The Daily Telegraph Sudoku and The Daily Telegraph Sudoku 2 at £5.99 each (plus 99p P&P per order) can be taken at Telegraph Books Direct on 0870 155 7222 (UK only).

Sudokulist on NEWSNIGHTTelegraph puzzle compiler Michael Mepham explains a sudoku to Newsnight reporter Greg Neale.This week the television world caught up with news that sudoku has become a newspaper phenomenon.Telegraph puzzle compiler Michael Mepham spent the day rushing from one TV studio to the next, spreading the word.

How to solve Su Doku: tips

गुइदेस
Roger Walker's tips were the first set I ever found. They take you from nothing into formal reasoning methods with colourful names like "three in a bed" at your own pace. What I liked best about this site are the animated tutorials.
Michael Mepham's article from the Daily Telegraph is by now somewhat of a classic. It is a very well-written systematic explanation of the basic techniques for solving Su Doku. It introduced the nomenclature "Ariadne's thread".
Angus Johnson's Simple Sudoku web site has a very fine page of Su Doku tips, starting with the most basic element: find the singletons, and progressing to complicated and bizarrely named rules of Su Doku logic like the "Swordfish".
Dan Rice's Sudoku Blog also does a good job of explaining the rules of inference, one per blog. Since it is a blog, it takes each rule by itself and spends time explaining it. It contains some of the best explanations I have seen of the more complex rules.
SuDokuHints has a nice tool: it can give hints on a puzzle, solve one step while telling you how it was done, or solve the full puzzle and explain each step. You can play games that it generates, or type your own puzzle into इत


My own two bits: a fiendish tutorial

Why another tutorial? Because you don't really need to know many tricks। I show this using a relatively hard puzzle by Wayne Gould, who creates puzzles for "The Times" of London. These are rated in difficulty from mild (the simplest) to fiendish (the one on the left). Gould claims that none of his puzzles ever need trial and error solutions. If you follow this example through you will find that you never really need very complicated tricks either. Another way of solving this very puzzle is given by Roger Walker in one of his tutorials. Our methods differ: I try to illustrate some often-used tricks in this example.
Step 1: Singletons: find the "loner"
hen you have eliminated the impossible whatever remains, however improbable, is the truth", said Sherlock Holmes. This is the principle by which we put the 3 in the top row. 1, 2 and 7 are eliminated by the clues in the row; 4, 5, 6 and 9 by those in the column, and 8 by the cell. This leaves the truth. I don't see it as very improbable; but one must give the master some poetic license. This rule may or may not be useful to begin things off, but it is indispensible in the end game (especially when it is coupled with the hidden loner rule of Step 8).
Step 2: Basic "slice and dice"

Let's see how to place a 4 in the bottom right cell. The blue lines show that it must go right into the bottom-most row, because the other two rows already have a 4 in them. These are the slices. Now one of the three squares in the bottom row of the cell already has a clue in it. The other square is eliminated by dicing. The green line shows that the middle column is ruled out, because it already contains a 4 in another cell. So we have finished the second move in a fiendish puzzle and found out what slicing and dicing is.
Step 3: Applied "slice and dice"


We can place two more 4s, shown in black in the picture on the left. This requires slice and dice exactly as before. Another example: we can place a 1 by slice and dice as shown in the picture on the right.
Step 4: Simple "hidden pairs"

Angus Johnson has this to say about hidden pairs: "If two squares in a group contain an identical pair of candidates and no other squares in that group contain those two candidates, then other candidates in those two squares can be excluded safely." In the example on the right, a 2 and a 3 cannot appear in the last column. So, in the middle rightmost cell these two numbers can only appear in the two positions where they are "pencilled in" in small blue font. Since these two numbers have to be in these two squares, no other numbers can appear there.
Step 5: "Locked candidates"
Angus Johnson again: "Sometimes a candidate within a cell is restricted to one row or column. Since one of these squares must contain that specific candidate, the candidate can safely be excluded from the remaining squares in that row or column outside of the cell." Since the hidden pair 2 and 3 prevent anything else from apearing in the first two columns of the middle rightmost cell, an 8 can only appear in the last column. Now we apply the locked candidates rule.


We want to place an 8 in the bottom right cell. The last column can be sliced out by the locked candidate rule. Other slicing and dicing is normal, leading to the placement of the 8 as shown.
Step 6: Bootstrap by extending the logic of "locked candidates"
To get to the first step of the bootstrap from the last picture shown above, we need to slice and dice to place an 8 in the center bottom cell. You must be an expert at this method by now, so I leave that in your capable hands.


The first element of the bootstrap is to place 8s in the middle row of cells. The picture on the left shows where the 8s must be placed in the middle left cell. The picture on the right shows the placement in the central cell.


Next we extend the logic of the locked candidates. The 5th and 6th rows must each have an 8: one of them has it in the middle left cell, and the other in the central cell. Therefore the 8 in the middle right cell cannot be in either of these rows. From what we knew before, the 8 must be in the top right corner square of the cell, as shown in the picture on the right. This is almost magical. Putting together imprecise information in three different cells, we have reached precise information in one of the cells.

And now the final step of the bootstrap is shown in the picture on the left. The placement of the 8 dictates that the 6 must be just below it, and therefore the 7 in the remaining square. The diabolical magic is complete: reason enough for this to be classified as a fiendish puzzle. One of Roger Walker's tutorials is a solution of precisely this puzzle, by a different route. But before going there, I invite you to try your hand at completing the solution which we have started upon here.
Step 7: The beginning of the end

The worst is over. We are now truly into the end game. First complete cell C entirely by the "loner" trick: filling 6, 5, 3 and 7 in that order. Next complete the cell F. Then finish the 7th column, place the 5 in the cell D, and complete that row, in order to get the picture on the left. We are more than half done. From now on common sense prevails: fill things in one by one. Don't panic, there are no sharks circling the boat. No swordfish either.
Step 8: "Hidden loner": almost not worth naming

The last rule, I promise. And it is hardly one, although you could call it the "hidden loner" rule. The only reason one should give it a name is that it fixes this very useful method in one's mind. So here is the example: In the 6th row there's more than one choice in each square. However there is only one place where the 5 can go (it is excluded from the squares with X's in them). So there is a loner hidden in this row: hence the name. I stop here, but you can go on to solve a fiendish puzzle by the simplest tricks exclusively.
Not so fiendish?

Mike Godfrey wrote to me to point out a much simpler way of solving this particular puzzle. After step 3, as before, one can fill in the 6 shown in blue in the figure here, by noting that all other numbers can be eliminated by requiring that they do not appear in the same row, column or block. After this the remaining puzzle can be solved by spotting singles.
Mike writes that this puzzle "is not too fiendish perhaps". Perhaps. But that opens up the question of how to rate puzzles. I haven't found much discussion of this aspect of the mathematics of Su Doku: partly because commercial Su Doku generators (by that I mean the humans behind the programs) are not exactly forthcoming about their methods, but also because the problem is not terribly well-defined. This is a wide open field of investigation.
From tricks to methods: the roots of mathematics
Constraint programming

The minimum Su Doku shown alongside (only 17 clues) requires only two tricks to solve: identifying hidden loners and simple instances of locked candidates. The key is to apply them over and over again: to each cell, row and column. The application of constraints repeatedly in order to reduce the space of possibilities is called constraint programming in computer science. "Pencilling in" all possible values allowed in a square, and then keeping the pencil marks updated is part of constraint programming. This point has been made by many people, and explored systematically by Helmut Simonis.
Non-polynomial state space
This is where much of the counting appears. Before clues are entered into a M×M Su Doku puzzle, and the constraints are applied, there are MM2 states of the grid. This is larger than any fixed power of M (this is said to be faster than any polynomial in M). If depth-first enumeration were the only way of counting the number of possible Su Dokus, then this would imply that counting Su Doku is a hard problem. Application of constraints without clues is the counting problem of Su Doku. As clues are put in, and the constraints applied, the number of possible states reduces. The minimum problem is to find the minimum number of clues which reduces the allowed states to one. The maximum problem is analogous.
Many known hard problems are of a type called nondeterministic-polynomial. In this class, called NP, generating a solution of a problem of size M takes longer than any fixed power of M, but given a solution, it takes only time of order some fixed power of M to check it (ie, a polynomial in M). If enumeration were the only way of counting the number of Su Doku solutions, then this would be harder than NP. If someone tells me that the number of Su Doku solutions is 6670903752021072936960, I have no way to check this other than by counting, which I know to takes time larger than polynomial in M. At present there is no indication that the counting problem of Su Doku is as easy as NP.
Trial-and-error: is Su Doku an NP complete problem?
The Su Doku problem is to check whether there is an unique solution to a given puzzle: the yes/no answer would usually, but not necessarily, produce the filling of the grid which we call a solution. It would be in NP if the time an algorithm takes to solve the M×M Su Doku problem grows faster than any fixed power of M. It is not known whether the Su Doku problem is in NP.
One sure fire way of solving any Su Doku puzzle is to forget all these tricks and just blindly do a trial-and-error search, called a depth-first search in computer science. When programmed, even pretty sloppily, this can give a solution in a couple of seconds. If we use this method on M×M Super Doku, then the expected run time of this program on the trickiest puzzles (called worst-case in computer science) would grow faster than any fixed power of M, but (of course) it is guaranteed to solve the puzzle. If trial-and-error were the only algorithm to solve any Su Doku puzzle whatsoever, and one were able to show that the state space of a puzzle grows faster than a fixed power of M, then this would prove that Su Doku is an NP problem.
Helmut Simonis has results which might indicate that trial-and-error is never needed, and a small bag of tricks with hyper arc consistency always answers the Su Doku question. However, one needs to ask how many times the consistency check has to be applied to solve the worst-case problem, and how fast this grows with M, in order to decide whether constraint programming simplifies the solution.
The controversy over trial-and-error
From this formal point of view, one can see the debate raging currently on Michael Mepham's web site and other discussion boards on Su Doku as an argument between the search enthusiasts and the constraint programming wallahs: with Mepham slowly giving ground in his defence of search. But does the debate just boil down to choosing which algorithm to use? Yes, if the Su Doku problem is easy (ie, in P) and constraint programming solves it faster. However, if Su Doku is hard, then there is a little more to it.
Backdoors: defining "satisfactory puzzles"
In many instances of NP complete problems, the average run time of programs can be substantially less than the worst-case. Gomes and Selman conjecture that this is due to the existence of "backdoors", ie, small sets of tricks which solve these average problems. Here human intuition (called heuristics in computer science) can help to identify the backdoors and often crack the nut faster than the sledge hammer of systematic algorithms. These I call "satisfactory puzzles". One of the open problems for Su Doku is to define precisely the nature of such backdoors, and the classes of problems which contain them.
Zen and the art of gardening
We have introduced elsewhere a method of counting Su Dokus by a depth first enumeration of trees (called the garden of forking paths). It is clear that some of the branches of these trees are much longer than the average. As M grows, this imbalance also grows (polynomially, or faster?). This is one way of visualizing the difference between the average case (satisfactory puzzles) and the worst case (diabolical puzzles). My challenge is a gardening problem: how do you make the trees come out balanced and symmetric? It is like a Zen puzzle: if you solve it, then you reduce human intuition (heuristics) to an algorithm; even if it is impossible you gain insight by contemplating the problem.

मठेमतिक्स/history of Sudoku

A completed Sudoku grid is a special type of Latin square with the additional property of no repeated values in any 3×3 block. The relationship between the two theories is now completely known, after Denis Berthier has proven in his recent book, "The Hidden Logic of Sudoku"[17], that a first order formula that does not mention blocks (also called boxes or regions) is valid for Sudoku if and only if it is valid for Latin Squares.
The number of classic 9×9 Sudoku solution grids was shown in 2005 by Bertram Felgenhauer and Frazer Jarvis to be 6,670,903,752,021,072,936,960[18] (sequence A107739 in OEIS) : this is roughly 0.00012% the number of 9×9 Latin squares. Various other grid sizes have also been enumerated—see the main article for details. The number of essentially different solutions, when symmetries such as rotation, reflection and relabelling are taken into account, was shown by Ed Russell and Frazer Jarvis to be just 5,472,730,538[19] (sequence A109741 in OEIS).
The maximum number of givens provided while still not rendering a unique solution is four short of a full grid; if two instances of two numbers each are missing and the cells they are to occupy form the corners of an orthogonal rectangle, and exactly two of these cells are within one region, there are two ways the numbers can be assigned. Since this applies to Latin squares in general, most variants of Sudoku have the same maximum. The inverse problem—the fewest givens that render a solution unique—is unsolved, although the lowest number yet found for the standard variation without a symmetry constraint is 17, a number of which have been found by Japanese puzzle enthusiasts,[20][21] and 18 with the givens in rotationally symmetric cells

Number puzzles first appeared in newspapers in the late 19th century[citation needed], when French puzzle setters began experimenting with removing numbers from magic squares. Le Siècle, a Paris-based daily, published a partially completed 9×9 magic square with 3×3 sub-squares in 1892.[22] It was not a Sudoku because it contained double-digit numbers and required arithmetic rather than logic to solve, but it shared key characteristics: each row, column and sub-square added up to the same number.
Within three years Le Siècle's rival, La France, refined the puzzle so that it was almost a modern Sudoku. It simplified the 9×9 magic square puzzle so that each row and column contained only the numbers 1–9, but did not mark the sub-squares. Although they are unmarked, each 3×3 sub-square does indeed comprise the numbers 1–9. However, the puzzle cannot be considered the first Sudoku because, under modern rules, it has two solutions. The puzzle setter ensured a unique solution by requiring 1–9 to appear in both diagonals.
These weekly puzzles were a feature of newspaper titles including L'Echo de Paris for about a decade but disappeared about the time of the First World War.[23]
According to Will Shortz, the modern Sudoku was most likely designed anonymously by Howard Garns, a 74-year-old retired architect and freelance puzzle constructor from Indiana, and first published in 1979 by Dell Magazines as Number Place (the earliest known examples of modern Sudoku). Garns's name was always present on the list of contributors in issues of Dell Pencil Puzzles and Word Games that included Number Place, and was always absent from issues that did not.[11] He died in 1989 before getting a chance to see his creation as a worldwide phenomenon.[11] It is unclear if Garns was familiar with any of the French newspapers listed above.
The puzzle was introduced in Japan by Nikoli in the paper Monthly Nikolist in April 1984[11] as Suuji wa dokushin ni kagiru (数字は独身に限る, Suuji wa dokushin ni kagiru?), which can be translated as "the digits must be single" or "the digits are limited to one occurrence." At a later date, the name was abbreviated to Sudoku by Maki Kaji (鍜治 真起, Kaji Maki?), taking only the first kanji of compound words to form a shorter version.[11] In 1986, Nikoli introduced two innovations: the number of givens was restricted to no more than 32, and puzzles became "symmetrical" (meaning the givens were distributed in rotationally symmetric cells).[10] It is now published in mainstream Japanese periodicals

see also---

List of Sudoku terms and jargon
Killer sudoku
Sudokube (3D variant)
Latin square
Logic puzzle
List of Nikoli puzzle types
Kakuro
Nonogram (aka Paint by numbers, O'ekaki)