Lay out a tree or forest.
[x,y,h,s] = treelayout(parent,post)
parent is the vector of parent pointers, with 0 for a root.
post is a postorder permutation on the the tree nodes.
(If post is omitted we compute it here.)
x and y are vectors of coordinates in the unit square at which
to lay out the nodes of the tree to make a nice picture.
Optionally, h is the height of the tree and s is the
number of vertices in the top-level separator.
See also ETREE4VHSWQ, TREEPLOT , ETREEPLOT .