Solution structure

Below is the structure of the solution:

problem.solution = {
    "container-0-id": {
        "item_id": [
            Xo, # item's X coordinate of the origin's placement
            Yo, # item's Y coordinate of the origin's placement
            w,  # item's width
            l,  # item's length
            # item's w, l will be interchanged
            # if the item was rotated while solving
        ],
        "item_id": [Xo, Yo, w, l],
        # ...
    },

    "container-1-id" : {
        "item_id": [Xo, Yo, w, l],
        "item_id": [Xo, Yo, w, l],
        # ...
    },

    # all the containers
}

The insertion point and the bin’s and item’s coordinate system can be seen here:

Please keep in mind, that origin of an item is it’s bottom left corner. Thus Xo, Yo are the coordinates of the item’s origin in the solution space (bin’s coordinates).

Warning

Be aware that the solution attribute is a mutable object. Creating a pointer on that object and making changes on the pointer will reflect on the solution attribute. Deepcopying that object is the safe way in this situation.