Tree datastructures

Tree datastructures is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

The following shows a tree of data with nesting denoted by visual levels of indentation:

RosettaCode
    rocks
        code
        comparison
        wiki
    mocks
        trolling

A common datastructure for trees is to define node structures having a name and a, (possibly empty), list of child nodes. The nesting of nodes captures the indentation of the tree. Lets call this the nest form.

# E.g. if child nodes are surrounded by brackets
#      and separated by commas then:
RosettaCode(rocks(code, ...), ...)
# But only an _example_

Another datastructure for trees is to construct from the root an ordered list of the nodes level of indentation and the name of that node. The indentation for the root node is zero; node 'rocks is indented by one level from the left, and so on. Lets call this the indent form.

0 RosettaCode
1 rocks
2 code
...

Task

1. Create/use a nest datastructure format and textual representation for arbitrary trees.
2. Create/use an indent datastructure format and textual representation for arbitrary trees.
3. Create methods/classes/proceedures/routines etc to:
   1. Change from a nest tree datastructure to an indent one.
   2. Change from an indent tree datastructure to a nest one
4. Use the above to encode the example at the start into the nest format, and show it.
5. transform the initial nest format to indent format and show it.
6. transform the indent format to final nest format and show it.
7. Compare initial and final nest formats which should be the same.

Note

• It's all about showing aspects of the contrasting datastructures as they hold the tree.
• Comparing nested datastructures is secondary - saving formatted output as a string then a string compare would suffice for this task, if its easier.
• The word "trolling" is substituted for the original, less appropriate, "golfing" in the tree above as golfing can be friendly fun! (just not for RC examples). Please update language examples appropriately.

Show all output on this page.

Go

<lang go>package main

import (

   "fmt"
   "io"
   "os"
   "strings"

)

type nNode struct {

   name     string
   children []nNode

}

type iNode struct {

   level int
   name  string

}

func printNest(n nNode, level int, w io.Writer) {

   if level == 0 {
       fmt.Fprintln(w, "\n==Nest form==\n")
   }
   fmt.Fprintf(w, "%s%s\n", strings.Repeat("  ", level), n.name)
   for _, c := range n.children {
       fmt.Fprintf(w, "%s", strings.Repeat("  ", level+1))
       printNest(c, level+1, w)
   }

}

func toNest(iNodes []iNode, start, level int, n *nNode) {

   if level == 0 {
       n.name = iNodes[0].name
   }
   for i := start + 1; i < len(iNodes); i++ {
       if iNodes[i].level == level+1 {
           c := nNode{iNodes[i].name, nil}
           toNest(iNodes, i, level+1, &c)
           n.children = append(n.children, c)
       } else if iNodes[i].level <= level {
           return
       }
   }

}

func printIndent(iNodes []iNode, w io.Writer) {

   fmt.Fprintln(w, "\n==Indent form==\n")
   for _, n := range iNodes {
       fmt.Fprintf(w, "%d %s\n", n.level, n.name)
   }

}

func toIndent(n nNode, level int, iNodes *[]iNode) {

   *iNodes = append(*iNodes, iNode{level, n.name})
   for _, c := range n.children {
       toIndent(c, level+1, iNodes)
   }

}

func main() {

   n1 := nNode{"RosettaCode", nil}
   n2 := nNode{"rocks", []nNode{{"code", nil}, {"comparison", nil}, {"wiki", nil}}}
   n3 := nNode{"mocks", []nNodeTemplate:"trolling", nil}
   n1.children = append(n1.children, n2, n3)

   var sb strings.Builder
   printNest(n1, 0, &sb)
   s1 := sb.String()
   fmt.Print(s1)

   var iNodes []iNode
   toIndent(n1, 0, &iNodes)
   printIndent(iNodes, os.Stdout)

   var n nNode
   toNest(iNodes, 0, 0, &n)
   sb.Reset()
   printNest(n, 0, &sb)
   s2 := sb.String()
   fmt.Print(s2)

   fmt.Println("\nRound trip test satisfied? ", s1 == s2)

}</lang>

Output:

==Nest form==

RosettaCode
    rocks
        code
        comparison
        wiki
    mocks
        trolling

==Indent form==

0 RosettaCode
1 rocks
2 code
2 comparison
2 wiki
1 mocks
2 trolling

==Nest form==

RosettaCode
    rocks
        code
        comparison
        wiki
    mocks
        trolling

Round trip test satisfied?  true

Python

Just arranges the standard lists and tuples for the datastructures allowing pprint to show the different arrangement of storage.

<lang python>from pprint import pprint as pp

def to_indent(node, depth=0, flat=None):

   if flat is None:
       flat = []
   if node:
       flat.append((depth, node[0]))
   for child in node[1]:
       to_indent(child, depth + 1, flat)
   return flat

def to_nest(lst, depth=0, level=None):

   if level is None:
       level = []
   while lst:
       d, name = lst[0]
       if d == depth:
           children = []
           level.append((name, children))
           lst.pop(0)
       elif d > depth:  # down
           to_nest(lst, d, children)
       elif d < depth:  # up
           return
   return level[0] if level else None
                   

if __name__ == '__main__':

   print('Start Nest format:')
   nest = ('RosettaCode', [('rocks', [('code', []), ('comparison', []), ('wiki', [])]), 
                           ('mocks', [('trolling', [])])])
   pp(nest, width=25)

   print('\n... To Indent format:')
   as_ind = to_indent(nest)
   pp(as_ind, width=25)

   print('\n... To Nest format:')
   as_nest = to_nest(as_ind)
   pp(as_nest, width=25)

   if nest != as_nest:
       print("Whoops round-trip issues")</lang>

Output:

Start Nest format:
('RosettaCode',
 [('rocks',
   [('code', []),
    ('comparison', []),
    ('wiki', [])]),
  ('mocks',
   [('trolling', [])])])

... To Indent format:
[(0, 'RosettaCode'),
 (1, 'rocks'),
 (2, 'code'),
 (2, 'comparison'),
 (2, 'wiki'),
 (1, 'mocks'),
 (2, 'trolling')]

... To Nest format:
('RosettaCode',
 [('rocks',
   [('code', []),
    ('comparison', []),
    ('wiki', [])]),
  ('mocks',
   [('trolling', [])])])