Is there an algorithm to find a spanning tree of an undirected grid graph which minimizes the number of turns in tree? A turn is when there are two edges connected to one vertex which have perpendicular directions.↵
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In this problem we have arbitrary set of cells in grid which form a connected graph (not only rectangles are considered).↵
Thus, set of cells may form concave areas and areas with holes↵
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For example, given a 4 x 4 grid graph (see image below), we want to find a spanning tree like that on the right (which has 6 turns) rather than that on the left (which has 14):↵
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![ ](https://i.stack.imgur.com/VjpTE.png)↵
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Ideas about approximate algorithms may be useful too.
↵
In this problem we have arbitrary set of cells in grid which form a connected graph (not only rectangles are considered).↵
Thus, set of cells may form concave areas and areas with holes↵
↵
For example, given a 4 x 4 grid graph (see image below), we want to find a spanning tree like that on the right (which has 6 turns) rather than that on the left (which has 14):↵
↵
![ ](https://i.stack.imgur.com/VjpTE.png)↵
↵
Ideas about approximate algorithms may be useful too.