java - merge adiacent rectangles into a polygon

Question

I have a set of rectangles that have the same width and height and are always adiacent. I know the position of all the vertices, each one having only 4. (because is a square).

Answer 1

Because your shape consists of rectangles only and they are always adjacent, the algorithm of merging is much simpler than it would be without those assumptions.

• Create a list of ALL edges from your rectangles. One rectangle has 4 edges.
• Let the Edge be a class with properly defined compareTo() and equals().
• Sort the edges list (uses compareTo).
• Iterate through the list. If the same edge is present in the list TWICE, remove them both from the list.
• The remaining edges are the edges of your polygon.