How to generate all possible tree with the total node of node N

I try to figu开发者_Python百科re out how to generate all possible tree from a set of unidentical node (Each node is labeled as A,B,C,D,... ) with the size of N. Anyhelp with this problem?

---

Eric Lippert explains how to do this.

Read the entire series; it's too long to copy here.