###### tags: `learning` `algorithm` `zxm`

Asking zxm for tree problems
===
## Suppose I have a tree

digraph G {
    nodesep=0.4;
    ranksep=0.5;
    {rank=same; B; E;}
    {rank=same; C; D;}
    {rank=same; F; G;}
    A -> B;
    A -> E;
    B -> C;
    B -> D;
    E -> F;
    E -> G
    } 
} 

## I want to go through all paths, starting from the root, ending at a leaf.
So, the print-out is

ABC
ABD
AEF
AEG

## I have come out with an approach by cutting off each leaf arrived.
However, this approach alters the exiting data structure. Even though I can avoid the change by copying the whole tree, there is extra usage of memory.