Do you know a slick way of pretty-printing a tree given its depth vector
representation?
A vector represents a tree if and only if it satisfies the following:
NB. Tree valid? First node is root node (depth 0), only one root node,
NB. and all nodes are exactly one deeper than their parent
tv=: 0&=@{. *. *./@(>&0)@}. *. 1 *./@:>: +/\^:_1
The goal is to produce a nice visualization given a valid depth vector. For
example, given (d=: 0 1 2 2 1 1 2 2 3), something like this would be ideal:
o
|-o
| |-o
| +-o
|-o
+-o
|-o
+-o
+-o
About the best I can do in a single line is this:
NB. Tree print
tp=: (, LF&,)/@({&' |o-')@((3&*@=/ |:@}.@(,/)@(,:"1&|:) 2&*@=/ +. >/) ~.)
tp d
o
|-o
| |-o
| | |-o
|-o
| |-o
| | |-o
|-o
| |-o
| | |-o
Trimming the branches, however, is giving me a lot of grief. Can you do better?
I am looking for terse one-liners but am open to alternative visualizations.
Producing segments of "trimmed branches" is a nice little sub-problem. It
corresponds to finding finding "catenaries", i.e. runs of integers capped on
the left and right by n, where the intervening integers "droop below" n, i.e.
satisfy (>:n).
Looking forward to your ideas!
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