As shown in Algorithm 2, CreateLeftChildTree is invoked
recursively to create the left child tree of a tree node in the binary
tree (shown in Fig. 7). If the residual space (lr wr hei)
cannot accommodate any box left in the box set B, Algorithm
2 returns an empty layer set. Otherwise, B is grouped into a
strip set S. Then a layer l is obtained by solving Formula (16).
Notice that l is parallel to the left side of the container. And
then the boxes that are included in l are removed from B. CreateLeftChildTree
is invoked again to create the left child tree of
the current tree node while CreateRightChildTree (described in