

Advanced Solving Sudoku Technique


Subset2 by us createclassicsudoku.com


Below is an example of using Subset2(a.k.a. Pair, or Naked Pair, or Naked Twins) to refine the candidate values of R7C1, R7C6, and R7C7. Blank/Empty Squares are marked with candidate values in red. 

Small Sudoku on 03/13/2018


Solve Small Sudoku on 03/13/2018 in a stepbystep style  
For the seventh row, R7C3 and R7C4 have same two candidate values {1, 4}. Therefore, it is safe to remove numbers 1 and 4 from the candidate numbers from other blank/empty squares in the seventh row. After we remove numbers 1 and 4 from R7C7's candidate values, R7C7 has one and only one candidate value (number 8) left. Therefore, R7C7 must be filled with number 8. 

For easy understanding, our Sudoku solver names three different categories of Subset2. 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


Subset2 by us createclassicsudoku.com


Below is an example of using Subset2(a.k.a. Pair, or Naked Pair, or Naked Twins) to refine the candidate values of R7C1, R7C6, and R7C7. Blank/Empty Squares are marked with candidate values in red. 

Medium Sudoku on 03/13/2018


Solve medium Sudoku on 03/13/2018 in a stepbystep style  
For the seventh row, R7C3 and R7C4 have same two candidate values {1, 4}. Therefore, it is safe to remove numbers 1 and 4 from the candidate numbers from other blank/empty squares in the seventh row. After we remove numbers 1 and 4 from R7C7's candidate values, R7C7 has one and only one candidate value (number 8) left. Therefore, R7C7 must be filled with number 8. 

For easy understanding, our Sudoku solver names 3 different categories of Subset2. 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?





