Sudoku is a logic-based
number placement puzzle. The objective is to fill a 9×9
grid so that each column, each row, and each of the nine 3×3
boxes (also called blocks or regions) contains the digits
from 1 to 9 only one time each. The puzzle setter provides
a partially completed grid. Completed Sudoku puzzles are usually
a type of Latin square with an additional constraint on the
contents of individual regions. Leonhard Euler is sometimes
incorrectly cited as the source of the puzzle, based on his
work with Latin squares. The modern puzzle was invented by
an American architect, Howard Garns, in 1979 and published
by Dell Magazines under the name "Number Place".
It became popular in Japan in 1986, after it was published
by Nikoli and given the name Sudoku, meaning single number.
It became an international hit in 2005.
ONLINE SUDOKU PUZZLES