Small chess problem

In addition to the well-known knight problem and women's problem, there are many other exciting questions in the world of chess. I touched on two small curiosities in a previous blog entry . If you deal with chess problems mathematically, you quickly find that mathematics provides very simple and illuminating answers to many questions.


As an example, I will now deal with the following problem: Look at an empty, regular chess board with 64 fields and place a white queen at any position \((x,y)\) . How many possible moves does the lady have?

Using the symmetry properties of the board, we transform every point \( (x,y) \in \{1,2,3,4,5,6,7,8\} \times \{1,2,3,4,5,6,7,8\} \) in its counterpart in the lower left quadrant \( (x',y') \in \{1,2,3,4\} \times \{1,2,3,4\} \) and choose the minimum \(z\) the two coordinates. Finally we get \(7\) horizontal, \(7\) vertical and \( 7 + 2\cdot(z-1)\) diagonal moves, which is why:

\[ f:\{1,2,3,4,5,6,7,8\} \times \{1,2,3,4,5,6,7,8\}, \\ f(x,y) = 2 \cdot \min(-|x-4,5|+4,5; -|y-4,5|+4,5)+19 \]

The inclined reader can easily extend the problem to chess boards of size \(n^2\) .

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