

Advanced Solving Sudoku Technique


SubsetPosition2 by us createclassicsudoku.com


Below is an example of using SubsetPosition2(a.k.a. Hidden Pair, or Hidden Twins) to refine the candidate values of R1C4 and R1C6 (the highlighted squares). Blank/Empty Squares are marked with candidate values in red. 

Hard Sudoku on 03/16/2018


Solve Hard Sudoku on 03/16/2018 in a stepbystep style  
For the first row, only R1C4 and R1C6 contains candidate values 3 and 4. Either number 3 in R1C4 and number 4 in R1C6, or number 4 in R1C4 and number 3 in R1C6. So we can conclude that numbers 3 and 4 must be in R1C4 and R1C6. And we can safely remove other numbers (besides 3 and 4) from R1C4 and R1C6's candidate values. 

For easy understanding, in our Sudoku solver, we call Subset2Row: an untaken number in a row only show up in one empty square as its candidate values, then this empty square must take the number. Subset2Col: an untaken number in a column only show up in one empty square as its candidate values, then this empty square must take the number. Subset2Box: an untaken number in a 3×3 box only show up in one empty square as its candidate values, then this empty square must take the number. 

How to find them?




Advanced Solving Sudoku Technique


SubsetPosition2 by us createclassicsudoku.com


Below is an example of using SubsetPosition2(a.k.a. Hidden Pair, or Hidden Twins) to refine the candidate values of R1C4 and R1C6 (the highlighted squares). Blank/Empty Squares are marked with candidate values in red. 

Hard Sudoku on 03/16/2018


Solve Hard Sudoku on 03/16/2018 in a stepbystep style  
For the first row, only R1C4 and R1C6 contains candidate values 3 and 4. Either number 3 in R1C4 and number 4 in R1C6, or number 4 in R1C4 and number 3 in R1C6. So we can conclude that numbers 3 and 4 must be in R1C4 and R1C6. And we can safely remove other numbers (besides 3 and 4) from R1C4 and R1C6's candidate values. 

For easy understanding, in our Sudoku solver, we call Subset2Row: an untaken number in a row only show up in one empty square as its candidate values, then this empty square must take the number. Subset2Col: an untaken number in a column only show up in one empty square as its candidate values, then this empty square must take the number. Subset2Box: an untaken number in a 3×3 box only show up in one empty square as its candidate values, then this empty square must take the number. 

How to find them?





