

Advanced Solving Sudoku Technique


XYWing by us createclassicsudoku.com
, and
humage.com
, and hodoku


Below is an example of using XYWingRowBox(one case of XYWing in our Sudoku solver, explained after the example) to refine the candidate values of R3C6 (the highlighted square that is not circled in red). Blank/Empty Squares are marked with candidate values in red. 

For R3C5,
Either way, either R3C9 or R1C4 will be number 1.


These above two possibilites rule out the possiblity that number 1 could be in R3C6. We can safely remove number 1 from R3C6. 

Hard Sudoku on 03/25/2018  
Solve Hard Sudoku on 03/25/2018 in a stepbystep style  
XYWing explained in a more detailed way: When one square with candidates {X, Y} is in the same row, column, or box as a second square with candidates {X, Z}; This square is also in the same row, column, or box as a third square with candidates {Y, Z}; Candidate Z can be eliminated from the squares that is both at the same row, column, or box as the second square, and at the same row, column, or box as the third square. Where Candidates (or Candiate Numbers, or Candidate Values) of an blank/empty square is a list of 'possible values' or candidates for this blank/empty cell. For easy understanding, we call XYWingRowBox, XYWingColBox, and XYWingRowCol in our Sudoku solver. XYWingRowBox: When one square with candidates {X, Y} is in the same row as a second square with candidates {X, Z}; This square is in the same box as a third square with candidates {Y, Z}; Candidate Z can be eliminated from the squares that is both at the same row, column, or box as the second square, and at the same row, column, or box as the third square. . XYWingColBox: When one square with candidates {X, Y} is in the same column as a second square with candidates {X, Z}; This square is in the same box as a third square with candidates {Y, Z}; Candidate Z can be eliminated from the squares that is both at the same row, column, or box as the second square, and at the same row, column, or box as the third square. XYWingRowCol: When one square with candidates {X, Y} is in the same row as a second square with candidates {X, Z}; This square is in the same column as a third square with candidates {Y, Z}; Candidate Z can be eliminated from the squares that is both at the same row, column, or box as the second square, and at the same row, column, or box as the third square. 

How to find them?




Advanced Solving Sudoku Technique


XYWing by us createclassicsudoku.com
, and
humage.com
, and hodoku


Below is an example of using XYWingRowBox(one case of XYWing in our Sudoku solver, explained after the example) to refine the candidate values of R3C6 (the highlighted square that is not circled in red). Blank/Empty Squares are marked with candidate values in red. 

For R3C5,
Either way, either R3C9 or R1C4 will be number 1.


These above two possibilites rule out the possiblity that number 1 could be in R3C6. We can safely remove number 1 from R3C6. 

Hard Sudoku on 03/25/2018  
Solve Hard Sudoku on 03/25/2018 in a stepbystep style  
XYWing explained in a more detailed way: When one square with candidates {X, Y} is in the same row, column, or box as a second square with candidates {X, Z}; This square is also in the same row, column, or box as a third square with candidates {Y, Z}; Candidate Z can be eliminated from the squares that is both at the same row, column, or box as the second square, and at the same row, column, or box as the third square. Where Candidates (or Candiate Numbers, or Candidate Values) of an blank/empty square is a list of 'possible values' or candidates for this blank/empty cell. For easy understanding, we call XYWingRowBox, XYWingColBox, and XYWingRowCol in our Sudoku solver. XYWingRowBox: When one square with candidates {X, Y} is in the same row as a second square with candidates {X, Z}; This square is in the same box as a third square with candidates {Y, Z}; Candidate Z can be eliminated from the squares that is both at the same row, column, or box as the second square, and at the same row, column, or box as the third square. . XYWingColBox: When one square with candidates {X, Y} is in the same column as a second square with candidates {X, Z}; This square is in the same box as a third square with candidates {Y, Z}; Candidate Z can be eliminated from the squares that is both at the same row, column, or box as the second square, and at the same row, column, or box as the third square. XYWingRowCol: When one square with candidates {X, Y} is in the same row as a second square with candidates {X, Z}; This square is in the same column as a third square with candidates {Y, Z}; Candidate Z can be eliminated from the squares that is both at the same row, column, or box as the second square, and at the same row, column, or box as the third square. 

How to find them?





