Soduko and KAMASUMA are LATIN games !!!
KAMASUMA and SUDOKU
KAMASUMA is the name of a large family of mathematical riddles,
closely related to the family of
LATIN
games, of which the most familiar member is
SUDOKU.
In SUDOKU, the objective is to fill a 9×9 grid so that each column, each row, and each of nine 3×3 boxes
contains the digits 1 to 9, once and only once. Note that if we add all the digits on each column,
each row and each of the nine 3x3 boxes, we get an equal sum of 1+2+….+9=45.
In the following, we use the word pattern to designate a series of places which should be filled with numbers.
The number of different number elements is equal to the number of sites or nodes of a pattern.
The column, row and 3x3 boxes of SUDOKU,
are each a pattern. In a LATIN arrangement each number
element appears once and only once, in each pattern. Thus, SUDOKU
is a LATIN game. In
SUDOKU, under Latin arrangement,
if we add all the elements on each pattern we get an equal sum, as mentioned above.
Note, however, that we may get equal sum for each pattern even though the arrangement is a non-Latin arrangement.
KAMASUMA example
An example of a KAMASUMA game is shown in Figure 1. In the quatrogram of Fig. 1,
there are only three different elements with a respective numerical value of 1, 2 and 3.
The quatrogram has three triangular patterns, each with three sites.
In the square grid of
SUDOKU every pattern site is shared by three patterns, a column pattern,
a row pattern and a 3x3box pattern. In contrast, in each triangular pattern of a quatrogram,
two site are shared with the neighboring triangles, while one site is not associated with any other
triangular pattern.
In the left quatrogram, the elements are arranged in a non-Latin arrangements.
Yet, the sum of elements in each pattern is the same sum of five, as designated by the numbers inside the triangle.
As a riddle, the player has to rearrange the elements so that an equal sum of six is obtained.
The reader is advised to find a solution before continue to read the current article.
As a hint we note that the desired arrangement is a Latin arrangement.
Fig. 1 A quatrogram KAMASUMA riddle with a solved
non-Latin arrangement and a Latin arrangement
SUB-LATIN ARRANGEMENT
Finding a Latin arrangement may be facilitated by the concept of a sub-Latin arrangement.
Suppose that one should place several elements of certain kind such that there is one and only one element
of that certain kind in each triangular pattern. In the case of quatrogram, such a sub-Latin arrangement
is possible with two, three or four elements. With two elements, for example the triple dot elements of Fig. 2,
both elements are placed on two opposing shared sites. In the case of three elements,
for example the single dot and the double dot elements of Fig 2, two elements are placed on non-shared sites
of adjacent triangles, while the third element is placed on a site shared by the remaining two triangles.
In a sub-Latin arrangement, four elements are placed on the four non-shared sites of the four triangles.
Fig. 2