What is Sudoku

Sudoku (Japanese: 数独, sūdoku), sometimes spelled Su Doku, is a logic-based placement puzzle, also known as Number Place in the United States. The aim of the canonical puzzle is to enter a numerical digit from 1 through 9 in each cell of a 9×9 grid made up of 3×3 subgrids (called “regions”), starting with various digits given in some cells (the “givens”). Each row, column, and region must contain only one instance of each numeral. Completing the puzzle requires patience and logical ability. Although first published in a U. S. puzzle magazine in 1979, Sudoku initially caught on in Japan in 1986 and attained international popularity in 2005.

Rules and terminology

The puzzle is most frequently a 9×9 grid, made up of 3×3 subgrids called “regions” (other terms include “boxes”, “blocks”, and the like when referring to the standard variation). Some cells already contain numbers, known as “givens” (or sometimes as “clues”). The goal is to fill in the empty cells, one number in each, so that each column, row, and region contains the numbers 1–9 exactly once. Each number in the solution therefore occurs only once in each of three “directions”, hence the “single numbers” implied by the puzzle’s name.

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