You are given a Sudoku puzzle with one and only
one solution, and your task is to fill the blank squares with numbers
1-9 so that each number 1-9 appear once and only once in each row,
column, and box.

OneChoice is the most basic
solving Sudoku technique. Once you find that only one number can be
filled in a blank square because all other numbers already appear in
its row, column, or box, we can fill this number to the empty square.

You are given a Sudoku puzzle with one and only
one solution, and the task is to fill the blank squares with numbers
1-9 so that each number 1-9 appear once and only once in each row,
column, and box.

One of the most basic solving
Sudoku techniques is Elimination (we call it as Row-Elimination,
Column-Elimination, and Box-Elimination in http://www.createclassicsudoku.com).
Once you find that in a mini-box (or row or column), a number can only
go to one empty square because all other empty squares cannot take
this number, we can fill it into the empty square.

Box-Elimination is one of the most basic solving Sudoku technique.
Once you find that in a mini-box (or row or column), a number can only
go to one empty square because all other empty squares cannot take
this number, we can fill it into the empty square. Box-Elimination -
In a mini-box (or row or column), a number can only go to one empty
square because all other empty squares cannot take it.

You are given a Sudoku puzzle with one and only
one solution, and the task is to fill the blank squares with numbers
1-9 so that each number 1-9 appear once and only once in each row,
column, and box.

One advanced solving Sudoku
techniques is Subset (we call it as Subset2Row/Subset2Col/Subset2Box,
Subset3Row/Subset3Col/Subset3Box, Subset4Row/Subset4Col/Subset4Box in
http://www.createclassicsudoku.com).
Once you find that in a row (or column or box), two empty squares
together share same candidate numbers, then we know that these two
numbers in this row will be in these two empty squares. Therefore, we
can remove these two numbers from other empty squares in this row (or
column or box). We call this method Subset2Row (or Subset2Col or
Subset2Box).

When solving a Sudoku puzzle, we mark
possible numbers for an empty square. These possible numbers are
called candidate numbers. If numbers 1, 3, 4 are the numbers that are
not yet shown in an empty square's row, column, or box, we call {1, 3,
4} as the empty square's candidate numbers.

When
three empty squares in a row (or column or box) together contain three
candidate numbers, these three numbers will be only in these three
empty squares, therefore we can remove these three numbers from other
empty squares in this row (or column or box). We call this method
Subset3Row (or Subset3Col or Subset3Box).

When
four empty squares in a row (or column or box) together contain four
candidate numbers, these four numbers will be only in these four empty
squares, therefore we can remove these four numbers from other empty
squares in this row (or column or box), and we call it Subset4Row (or
Subset4Col or Subset4Box).

You are given a Sudoku puzzle with one and only
one solution, and the task is to fill the blank squares with numbers
1-9 so that each number 1-9 appear once and only once in each row,
column, and box.

One advanced solving Sudoku
techniques is SubsetPosition (we call it as SubsetPosition2,
SubsetPosition3, SubsetPosition4 in http://www.createclassicsudoku.com).
Once you find that in a row (or column or box), two untaken numbers
only appear in two empty squares, then these two empty squares will be these two numbers.
Therefore, we can remove all other candidate numbers from these two empty squares. We call
this method SubsetPosition2Row (or SubsetPosition2Col or SubsetPosition2Box).

When solving a
Sudoku puzzle, we mark possible numbers for an empty square. These
possible numbers are called candidate numbers. If numbers 1, 3, 4 are
the numbers that are not yet shown in an empty square's row, column,
or box, we call {1, 3, 4} as the empty square's candidate numbers.

Once you find that in a row (or column or box), three untaken numbers
only appear in three empty squares, then these three empty squares will be these three numbers.
Therefore, we can remove any other candidates from these three squares. We call
this method SubsetPosition3Row (or SubsetPosition3Col or SubsetPosition3Box).

Once you find that in a row (or column or box), four untaken numbers
only appear in four empty squares, then these two empty squares will be these four numbers.
Therefore, all other candidates can be removed from these four empty squares. We call
this method SubsetPosition4Row (or SubsetPosition4Col or SubsetPosition4Box).

You are given a Sudoku puzzle with one and only
one solution, and the task is to fill the blank squares with numbers
1-9 so that each number 1-9 appear once and only once in each row,
column, and box.

One advanced solving Sudoku
techniques is Interaction (we call it as InteractionRowBox,
InteractionColBox, InteractionBoxRow, InteractionBoxCol in http://www.createclassicsudoku.com).

InteractionRowBox - In a row, a number only goes to columns within a mini-box.
We can eliminate the possibility of this number in
other empty squares in this mini-box.

InteractionColBox - In a column, a number only goes to rows within a mini-box.
We can eliminate the possibility of this number in
other empty squares in this mini-box.

InteractionBoxRow - In a box, a number only goes to squares within a row.
We can eliminate the possibility of this number in
other empty squares in this row.

InteractionBoxCol - In a box, a number only goes to squares within a column.
We can eliminate the possibility of this number in
other empty squares in this column.

You are given a Sudoku puzzle with one and only
one solution, and the task is to fill the blank squares with numbers
1-9 so that each number 1-9 appear once and only once in each row,
column, and box.

One advanced solving Sudoku
techniques is X-Wing (we call it as DoubleRowsOneDigitCheck,
DoubleColsOneDigitCheck, TripleRowsOneDigitCheck, TripleColsDigitCheck
in http://www.createclassicsudoku.com).

DoubleRowsOneDigitCheck - In two rows, a number will be in two columns
(forms a X-wing for the two possibilities),
this number can be removed from other empty squares
in these two columns.

DoubleColsOneDigitCheck - In two columns, a number will be in two rows
(forms a X-wing for the two possibilities),
this number can be removed from other empty squares
in these two rows.

TripleRowsOneDigitCheck - In three rows, a number will be in three columns,
this number can be removed from other empty squares
in these three columns.

TripleColsOneDigitCheck - In three columns, a number will be in three rows,
this number can be removed from other empty squares
in these three rows.

You are given a Sudoku puzzle with one and only
one solution, and the task is to fill the blank squares with numbers
1-9 so that each number 1-9 appear once and only once in each row,
column, and box.

xyWingRowBox - If a common friend causing two empty squares (one square is in the same row as this common friend, another one is in the same box as this common friend),
one of them has to filled with a number, we can
remove this number from the common friends
of this two empty squares.

xyWingColBox - If a common friend causing two empty squares (one square is in the same column as this common friend, another one is in the same box as this common friend),
one of them has to filled with a number, we can
remove this number from the common friends
of this two empty squares.

You are given a Sudoku puzzle with one and only
one solution, and the task is to fill the blank squares with numbers
1-9 so that each number 1-9 appear once and only once in each row,
column, and box.

If we guess an empty square to be a number, and we found
there is a conflict (e.g., two same numbers in a row/column/box or an
empty square has ZERO candidate numbers). then we can remove these
guessed number from the empty square's candidate numbers. We call this
method GuessElimination

You are given a Sudoku puzzle with one and only
one solution, and the task is to fill the blank squares with numbers
1-9 so that each number 1-9 appear once and only once in each row,
column, and box.

One beyond expert solving Sudoku
techniques is exhaustive search (we call it ExhaustiveSearch in http://www.createclassicsudoku.com).
You solve the Sudoku by searching all the possible combinations. You will need a piece of paper to remember which
combinations you have tried, and which are not. This is the most challenging solving Sudoku technique.