Hints & Tips for Sudoku
Sudoku is a number puzzle based on a nine-by-nine grid divided by three-by-three blocks. Each block contains cells for the numbers one through nine, with some already filled in. The goal is to fill in the rest of the cells with one through nine so they occur only once in each row, column and group of three-by-three cells.
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Easy Rows and Numbers
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Start with the rows, columns or regions that have the most numbers filled in. Similarly, if there are already eight "ones" on the board but only two "fives," finding the last "one" first will be easier than finding the "fives." Use process of elimination to find which columns or rows need the least work to fill in.
Locked Candidates
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Within each three-by-three grid, you'll sometimes find a number restricted to a specific column or row. While you may not know exactly which cell the number goes in, this is a "locked candidate" because you have the number locked in to a specific row or column. You know the number can't go in that column in another grid because that would put two of the same number in the same column. This means you can eliminate the possibility of the locked candidate number going anywhere in the same column or row.
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Overlapping Numbers
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Look for patterns where a row and connecting column both need the same number. For example, if the bottom row still needs a one, four and seven, and the left column needs a three, four and eight, you know the four has to go where the column and row meet.
Using Pencil
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If you're playing a game of Sudoku on paper, use a pencil. With a pencil, you can easily fill-in and erase each cell's possibilities, making it easier to deduce which numbers go where. Write the possibilities smaller than numbers you think you're sure of so it's easy to distinguish between your answers and possibilities.
Checking Your Work
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If just one number is in the wrong cell, it will throw off the entire puzzle and make solving it impossible. When you write a new number down, scan the entire puzzle vertically and horizontally for the same number. Also, search the three-by-three box the number is in. If you find the number again in the same column, row or box, one of them is wrong. When you've completed a row, column or box, the added sum of each should equal 45.
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References
Resources
- Photo Credit Sudoku image by Claude Wangen from Fotolia.com
