This is a commentary on the solution from Benjamin Qi. from permutation to tree generation Before we go into the solution of this problem it is good to be able to understand how to create a tree using a permutation. First how does a permutation \(a\) translate into a tree? Think of \(a[i]\) as the time in which node \(i\) is inserted to the tree. We’ll use the following \(a=42315\) for illustration.