There are different solution methods in understanding the Sudoku puzzle.
A line of attack in solving this puzzle comprises a sequence of three processes:
scanning, marking up, and assessment. Scanning is carried out in the beginning.
This includes the process of elimination. Digits are scanned in order of their
occurrence. All the numbers should be checked systematically by scanning the
sections’ region, row, and column for values in order to see which is
left as a possibility.

Marking up is a method used when no further digits can be determined by making
candidate digits in the blank cells. Enlisting pencil dots in a single cell
is a more likely way of putting it through. When candidate numbers are excluded,
markings are then erased.

In assessment, there are two lines of approach, the what-if and candidate
exclusion. In candidate exclusion, candidate digits are eliminated successively
from cells to leave just one selection or choice. In what-if approach, a guess
is made; only two candidate digits are designated. One cannot deny that tallying
of regions, rows, and columns is pain in the eyes. In scripting candidate
digits into unfilled cells can be time consuming and the what-if approach
can be perplexing unless well thought-out.

With that regard, keeping track of moves in succession all out once is important.
Of course there are three methods with varying degrees: The base methods that
include the searching number method and ‘per cell’ method, and
the ‘pencil mark’ method; advance methods that include the candidates
reduction, the locked candidate (in a block, row, or column), the naked pair,
triple, and quad, and the hidden pair and triple; extreme methods that include
the X-wing, the swordfish, and the XY-wing.

In base method, one should start simply by inserting missing digits and examining
particular rows and crossings with other blocks or columns. By using ‘pencil
mark’ one would be able to recall remaining candidate digits presumed
for that cell. With use of base method, one would be able to locate single
exact number to be assigned. In advance method, relationships in between candidate
digits in distinct cells were perceived. Finally, in extreme method, observed
were the associations of the candidate digits beyond its particular region.

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