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Frequently Asked Sudoku Questions

When was sudoku invented, and who invented it?

Some accounts attribute the game to a Swiss mathematician, Leonhard Euler in the late 1700s. The four lines that create the 9x9 blocks were added later. The name Sudoku originates from Japan and is translated to mean solitary number. A very similar puzzle called Number Place was published in America in the late 1970's and in 1984 a Tokyo publisher saw the Number Place puzzle and began producing a Sudoku magazine.


Can a puzzle have more than one correct solution?

No. Every Sudoku puzzle has one and only one correct solution.



Can I change or move the numbers that are already on the puzzle when I start it?

The pre-filled boxes are sometimes referred to as "givens". No, you cannot change or move any of the givens in a Sudoku puzzle.



Do I need to be smart in math to be able to get the right answer?

No. After all, you're not performing any operations on the numbers, like adding, subtracting or multiplying. Sudoku is solved by using logic and patience. It's basically a process of elimination.



Isn't sudoku really a trial and error puzzle?

No, it's not a trial and error game, although some players say they use trial and error. The best way to solve the puzzle is to eliminate all but one possible number for each box – guessing can actually waste time.



When I start a new puzzle, where should I begin?

You can solve a Sudoku puzzle in any order or fashion you like. The natural human tendency may be to start in the upper-left corner of the grid and work down and to the right. This is rarely the best route to follow. Many players like to look for the rows, columns, and blocks that contain the most "givens". As a player becomes more experienced it usually gets easier to spot a good starting place because the eye gets better trained to see matching numbers in adjacent rows, columns and blocks.



What do I do if I make a mistake and end up with the same two numbers in a row, column or block?

You only have two choices – either start over or try to find and correct the mistake. In most cases, players can back themselves into a corner where most of the puzzle has been completed, but suddenly there is no correct place to put a number to complete the row, column or block. This problem is most likely the result of having two of the same numbers in a row, column or block. This might be the only place where trial and error might help, because in order to change the duplicate number you'll need to change at least one other number to bring the puzzle back in line with the rules.



Are there other variations of the game besides the standard 81 box grid?

Yes, there are several variations. A few examples are: · Diagonal Sudoku - adds the two main diagonals of the basic 9x9 box – so the numbers along the diagonals must also run 1 through 9 and cannot repeat. · High Five Sudoku - is a version available in some Sunday newspapers that uses five 9x9 grids that overlap each other. · Even-Odd Sudoku - uses boxes of two different colors – one color box must contain only odd numbers and the other color must contain only even numbers – all of the other Sudoku rules apply.



How long does it take to complete a puzzle?

That depends on the skill of the player and the difficulty of the puzzle. A basic Sudoku grid with plenty of givens could be completed in just a few minutes, whereas a more difficult basic puzzle or a more difficult variation, like High Five Sudoku can take several hours. As you get better at the game, your times will improve.



What kind of person would make a good sudoku player?

Just about anyone. Players come from all walks of society. The game involves logic and the process of elimination, so it takes some deductive reasoning and plenty of patience. Beginners should not be discouraged if they're unable to complete a puzzle – just keep trying!



Are Sudoku tournaments held?

Yes. You can find information about Sudoku tournaments on the Internet. The first World Championship Sudoku Tournament was held in Lucca, Italy in March of 2006. The winner was an accountant from the Czech Republic, 2nd and 3rd place were one by US citizens - a Harvard University graduate student and a software engineer from Google. The finalists had to compete by solving 45 puzzles over two days. A number of Sudoku variations were used in addition to the basic 81 block grid.