Daily sudoku - frequent asked questions:

 

 

What does “Sudoku” mean?

The correct pronunciation in Japanese is “su-doku” the literal meaning of it is “the number that is single”.

The strategy for solving a puzzle may be regarded as comprising a combination of three processes: scanning, marking up, and analysing.

Does it require any previous knowledge?

Sudoku does not require any knowledge of mathematics or any to be solved. However, Sudoku does require logic and reasoning. The use of numbers offers one method of identification – letters, colors, symbols, photos or anything else could offer identifiers for the slots.

What are the rules of Sudoku?

The simple basic rule is to complete the grid with different numbers in every row, column & slot. The existing numbers given in the grid are not to be changed or moved.

Fill in the grid so that every row, every column, and every 3x3 box contains the digits 1 through 9. "

How to solve a Suduko - Scanning

Scanning is performed at the outset and periodically throughout the solution. Scans may have to be performed several times in between analysis periods. Scanning comprises two basic techniques, cross-hatching and counting, which may be used alternately:

  • Cross-hatching, being the scanning of rows (or columns) to identify which line in a particular region may contain a certain number by a process of elimination. This process is then repeated with the columns (or rows). For fastest results, the numbers are scanned in order of their frequency. It is important to perform this process systematically, checking all of the digits 1-9.
  • Counting 1-9 in regions, rows, and columns to identify missing numbers. Counting based upon the last number discovered may speed up the search. It also can be the case (typically in tougher puzzles) that the value of an individual cell can be determined by counting in reverse – that is, scanning its region, row, and column for values it cannot be to see which is left.

Advanced solvers look for "contingencies" while scanning - that is, narrowing a number's location within a row, column, or region to two or three cells. When those cells all lie within the same row (or column) and region, they can be used for elimination purposes during cross-hatching and counting . Particularly challenging puzzles may require multiple contingencies to be recognized, perhaps in multiple directions or even intersecting - relegating most solvers to marking up (as described below). Puzzles which can be solved by scanning alone without requiring the detection of contingencies are classified as "easy" puzzles; more difficult puzzles, by definition, cannot be solved by basic scanning alone.

 

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