Fig. 2.

Graphical representation of the reasonable search space. The root node represents the initial tree t; each node on row k represents a restricted tree with k leaves removed. Each node is annotated by the removing set (top) and a diameter pair of the induced tree (bottom). Each edge in the graph represents a reasonable removal. The path from the root to any node corresponds to a reasonable removing chain. Each row k in the graph gives the k-removing space of t (${\mathcal{S}}_k\left(t\right)$)