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Some packing problems

**The orthogonal packing problem (OPP). **
The problem consists in determining if a set of rectangular items can be packed within a given rectangular container, so as that no two items
overlap.
The widths and heights of the items are given.
The width and height of the container are given.
The items can not be rotated and their sides are orthogonal to the sides of the container (this explains why the width and the height are
differentiated).

**The strip packing problem (SPP). **
The height of the container is not fixed.
The problem consists in packing the items in the container minimizing the height..

** Knapsack 2D. **
The problem is to pack items from a given set S in a unique container C so as to maximize the cumulated costs of the items.
In many cases the cost is the area, and then the problem consists in maximizing the occupied area.

** Bin packing 2D. **
All the items must be packed in identical containers, using the fewest possible containers.