Sudoku Tips
Sudoku grid consists of 81 squares divided into nine columns marked a through i, and nine rows marked 1 through 9. The grid is also divided into nine 3x3 sub-grids named boxes which are marked box 1 through box 9.
Scanning techniques
The easiest way starting a Sudoku puzzle is to scan rows and columns within each triple-box area, eliminating numbers or squares and finding situations where only a single number can fit into a single square. The scanning technique is fast and usually sufficient to solve easy puzzles all the way to the end. The scanning technique is also very useful for hard puzzles up to the point where no further progress can be made and more advanced solving techniques are required. Here are some ways of using scanning techniques:
1. Scanning in one direction:
In our first example we will focus on box 2, which like any other box in Sudoku must contain 9. Looking at box 1 and box 3 we can see there are already 9s in row 2 and in row 3, which excludes the two bottom rows of box 2 from having 9. This leaves square e1 as the only possible place into which 9 can fit in.
2. Scanning in two directions:
The same technique can be expanded by using information from perpendicular rows and columns. Let’s see where we can place 1 in box 3. In this example, row 1 and row 2 contain 1s, which leaves two empty squares in the bottom of box 3. However, square g4 also contains 1, so no additional 1 is allowed in column g. This means that square i3 is the only place left for 1.
3. Searching for Single Candidates:
Often only one number can be in a square because the remaining eight are already used in the relevant row, column and box. Taking a careful look at square b4 we can see that 3, 4, 7 and 8 are already used in the same box, 1 and 6 are used in the same row, and 5 and 9 are used in the same column. Eliminating all the above numbers leaves 2 as the single candidate for square b4.
4. Eliminating numbers from rows, columns and boxes:
There are more complex ways to find numbers by using the process of elimination. In this example the 1 in square c8 implies that either square e7 or square e9 must contain 1. Whichever the case may be, the 1 of column e is in box 8 and it is therefore not possible to have 1 in the centre column of box 2. So the only square left for 1 in box 2 is square d2.
5. Searching for missing numbers in rows and columns:
This method can be particularly useful when rows (and columns) are close to completion. Let’s take a look at row 6. Seven of the nine squares contain the numbers 1, 2, 3, 4, 5, 8 and 9, which means that 6 and 7 are missing. However, 6 cannot be in square h6 because there is already 6 in that column. Therefore the 6 must be in square b6.
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Sudoku Levels
How to define the difficuly of a sudoku puzzle?Multiple parameters should be taken care of:
the size of the sudoku: the smaller, the easier
the number of givens: the more givens, the easier the sudoku - although the number of givens doesn't really tell about the difficulty the position of the givens As surprising as it may be, two sudoku grids can have the same cells filled with givens and at the same time be totally different, difficulty speaking.
Therefore the conclusion is that the complexity of a puzzle can only be measured in analyzing the methods required to solve it, and this analysis may differ from one person to another. That is what makes Sudoku so interesting!
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History of sudoku
However, Sudoku how we know it today was born in 1979, when Howard Garns creates his first puzzle. The Dell Magazines company puts it into a new-yorker magazine, the Dell Pencil Puzzles and Word Games, under the name Number Place.
The Nikoli company introduces sudoku in Japan in April 1984 in the Monthly Nikolist magazine and names it Suji wa dokushin ni kagiru (that translates to « the number must be unique » or « occurs once »), which litteraly means « alone » ou « single ». Later, the name changes to « Sudoku », following the tradition of making smaller words in taking the first kanji of the expression.
In 1986, Nikoli adds two elements that will make the game popular: the number of given cells is 30 at most and puzzles must look symmetric.
As you may see, the grids on Live Sudoku still follow these rules.
Today, most japanese papers have their sudoku page, even if it is within another name.
Sudoku quickly became very popular on the Internet ; Live Sudoku gives you original puzzles and online playing, classified through different difficulty levels.
It should be funny to notice that Japanese developed the Sudoku because their alphabet has too many signs to make 'industrial' crosswords.
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The rules of the game
You must fill each cell with numbers going from 1 to 9, with the restriction that one single number can only appear once in the same row, in the same column, or in the same box of 3x3 cells.
At the game start, twenty to thirty numbers are already given and you have to find all the others. Indeed, a valid starting grid can only lead to one and only one solution. To find the missing numbers, you must use logic and observation.
Many variants can be played, only changing the quantity of rows or columns. You can try on Live Sudoku all the combination of grids from kids sudoku to giant sudoku.
To ease your game, we give you a few tips and tricks quite easy to remember. Use them wisely, and you will be able to complete your sudokus faster!
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What is Sudoku?
More than a funny little game, this is a real phenomenon. English people are crazy about it, japanese went crazy way before, even if they are not the real inventors of this logic game.
Sudoku is popular, that's obvious: every paper now has its "daily" puzzle, and readers are doing them every day. After England, the rush took Australia, United States, and then the rest of the world.
With its quite basic rules, although requiring much observation and reflexion, the Sudoku is perfect for all ages, thanks to customizable difficulty levels.
Advised by doctors, the Sudoku is excellent if you want to stimulate yourr brain or occupy a few dead hours.
And if you ever get bored with the classic game, there are plenty of variants that Live Sudoku gives you for free.
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