Whether you are having a vacation or recovering from the hospital, Sudoku is a perfect number game for you! It develops your logical reasoning ability, patience, your concentration to solve problems, and helps you build confidence.

In my earlier blog “How to Design a Sudoku Within Minutes,” I talked about the idea of designing a Sudoku in the exact REVERSE WAY of solving a Sudoku. If you want to create a Sudoku, you must be able to solve a Sudoku! In this article, I am going to show you two basic methods to solve an easy Sudoku – OneChoice and Elimination.

OneChoice: An empty square can only be filled with a number because all other numbers are taken in its row, column, or box.

Use OneChoice method to infer the number for square R1C9

For the highlighted square, which number must it be? 1 is taken in the ninth column, 2 is taken in the first row, 3 is taken in the third 3×3 box, 4 and 5 are taken in the first row, 6 is taken in the ninth column, 7 and 8 are taken in the first row. Therefore, only number 9 is not taken. The empty square at R1C9 (first row, ninth column) must be filled with number 9.

Elimination: An untaken number in a row/column/box can only be filled in an empty square in that row/column/box because all other empty squares are ruled out.

Where do I put number 6 in the seventh box? Elimination: In the 7^{th} box, only R8C2 can be filled with number 6.

In the 7^{th} box, number 6 is untaken. Where can we put it? The first column already contains number 6, therefore, R7C1, R8C1, R9C1 can not be filled with number 6. The seventh row already contains number 6, therefore, R7C2, R7C3 can not be filled with number 6. The third column already contains number 6, therefore R9C3 can not be filled with number 6. Therefore, in the seventh 3×3 box, number 6 can only be filled in R8C2.

Yaling Zheng, Ph.D., founder of https://www.createclassicsudoku.com, received a doctorate degree from the University of Nebraska-Lincoln, where her studies focused on constraint programming and machine learning. She lives in Greater Cleveland/Akron.
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