game of placing numbers in squares, using very simple rules of logic
Fill all the blank squares in a game with the correct numbers.
In a 9 by 9 square Sudoku game:
Every row of 9 numbers must include all digits 1 through 9 in any order
Every column of 9 numbers must include all digits 1 through 9 in any
Every 3 by 3 subsection of the 9 by 9 square must include all digits 1
Every Sudoku games begins with a number of squares already filled in,
and the difficulty of each game is largely a function of how many
squares are filled in.
The more squares that are known, the easier it is to figure out which
numbers go in the open squares.
As you fill in squares correctly, options for the remaining squares are
narrowed and it becomes easier to fill them in.
scan the rows and columns to determine where a certain number should be
The 7 is
required in the top right corner determined by first analyzing its 9
The only numbers missing in the region are a 5 and a 7.
However, putting a 5
in the top right box
would conflict with the 5
already in the top
row and the rightmost column. The
7 would not conflict with any of the given numbers.
Once the 7
is filled in, only a 5
can go beneath it
as all digits from 1 through 9 must be represented in the region.
Now turn to the two remaining open boxes in the right
column - these must include a 2
and a 4 as
the column's digits must represent 1 through 9.
One of these options, placing the 4
beneath the 1,
would lead to a conflict with the 4 already in that horizontal row, so
the only option for this box must be a 2.
Options for boxes are often not that easy to deduce.
Each step makes the next step easier by narrowing possibilities.
Every solved box makes filling the next box a little bit easier.