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Sudoku is a logic game played on a 9x9 grid using the digits 1 through 9. This grid is further subdivided into nine 3x3 boxes. The goal is to fill in the grid with digits such that one and only one of each digit 1 through 9 appear in every row, column, and box.
At logicgamesonline.com, you enter a digit in a sudoku grid cell by moving your mouse over that cell and then typing the digit. Typing anything other than a digit will erase the cell.
Play sudoku now or read on for some tips on solving sudoku.
Most sudoku boards can be solved using logic to deduce where digits should be placed. Use the fact that each digit can only be placed in each row, column, and box once.
In the following sudoku, the first and third columns both have 4s in them. The lower left box still needs a 4. Since it can't be placed in the first or third column of the sudoku, there is only one remaining cell in which to place it. At other times, you can use the same technique but combining rows and columns, as is done in the second sudoku image to place a 6.
This technique involves checking off all the possible digits that can go in a particular cell of the sudoku until only one remains. For example, look at the lower right corner of the center box. It can't be a 1, 3, 4, 5, 8, or 9 since those digits already occur in the box. It can't be a 2 or 6, since those digits occur in the same column of the sudoku. So, it must be a 7.
Sometimes you can't place a digit in a specific cell of the sudoku, but know that it must go in one of two or three different positions. In the sudoku board below, you can see that a 6 must go in one of the lower 2 cells on the right side of the bottom left box of the sudoku. Since the 6 in that box must be in the third column, we know the 6 in the middle box on the left side can't be in the third column. Using this and two other sixes, we can place the 6 in the center of that box of the sudoku. The same technique is used to place the 5 in the middle right box in the second sudoku image.
Click here for the solution to this sudoku.
Often the above techniques are enough to finish the sudoku, as is the case with this sudoku. In very difficult sudokus, you may get to a point where you can no longer logically deduce any more digits. When you get to this point, it is necessary to pick a cell that you have reduced to two possibilities. Choose one of the possibilities and work it out. If you have picked the wrong one, you will eventually end up with a contradiction - that is, to continue you will need to place two of the same digit in a row, column, or box in the sudoku. You can then go back and know that the other possibility was the correct one. If, on the other hand, everything works out, then you have picked the correct number for that cell and you have finished the sudoku.
