Generating a tree from nested set - ruby-on-rails

Question

I am looking to display a html tree from nested set data.
As the displayed tree does not always display all branches the leaf nodes cannot be identified by subtracting the lft & rgt values.
1 Drinks 27
/ | \
2 Coffee 3 4 Tea 20 21 Milk 26
/ \
5 Black 8 9 Green 19
/ \
10 China 14 15 Africa 18
I was looking to adapt the following code:
How to render all records from a nested set into a real html tree
Solution:
Happy to receive code improvement suggestions :)
def tree_from_set(set, start_level)
buf = "<ul>"
parent = []
prev = set[start_level]
set[start_level+1..-1].each do |node|
if node.lft.between?(prev.lft, prev.rgt)
# Previous was the parent
buf << open_parent_tag(prev)
parent.push(prev)
else
if node.lft.between?(parent.last.lft, parent.last.rgt)
#Previous was a child
buf << leaf_tag(prev)
else
buf << leaf_tag(prev)
begin
buf << "</ul></li>"
parent.pop
end until parent.empty? or node.lft.between?(parent.last.lft, parent.last.rgt)
end
end
prev = node
end
buf << leaf_tag(prev)
begin
buf << "</ul></li>"
parent.pop
end until parent.empty?
buf << "</ul>"
buf.html_safe
end
def open_parent_tag(node)
%{ <li>
#{link_to(node.name, node)}
<ul>
}
end
def leaf_tag(node)
content_tag(:li, link_to(node.name, node))
end

Answer 1

I used this function, but on php, not on ruby:
<?php
//nested sets data ordered by left
$data = array(
array("left" => 1, "right" => 10, "name" => "P0"),
array("left" => 2, "right" => 7, "name" => "P1"),
array("left" => 3, "right" => 4, "name" => "P11"),
array("left" => 5, "right" => 6, "name" => "P12"),
array("left" => 8, "right" => 9, "name" => "P2")
);
//Converter function gets nested sets array and returns nested php array
function nest($arrData){
$stack = array();
$arraySet = array();
foreach( $arrData as $intKey=>$arrValues) {
$stackSize = count($stack);
while($stackSize > 0 && $stack[$stackSize-1]['right'] < $arrValues['left']) {
array_pop($stack);
$stackSize--;
}
$link =& $arraySet;
for($i=0;$i<$stackSize;$i++) {
$link =& $link[$stack[$i]['id']]["children"]; //navigate to the proper children array
}
$tmp = array_push($link, array ('item'=>$arrValues,'children'=>array()));
array_push($stack, array('id' => $tmp-1, 'right' => $arrValues['right']));
}
return $arraySet;
}
//Print result
printArray(nest($data));
function printArray($array){
echo "<ul>";
foreach ($array as $row){
$children = $row['children'];
echo "<li>";
echo $row['item']['name'];
if (!empty($children)) printArray($children);
echo "</li>";
}
echo "</ul>";
}
?>

Answer 2

Managed to convert it to C++ for those who was looking for it like I was.
readDataBaseData(QVector<NodeData> &data, DBNode *node)
{
if(data.size() < 1){
return;
}
QVector<QPair<NodeData, int>> stack;
DBNode* arrayRes = node;
foreach (NodeData curArrDataItem, data) {
int stackSize = stack.size();
while(stackSize > 0 &&
stack.at(stackSize - 1).first.right < curArrDataItem.left){
stack.pop_back();
stackSize--;
}
DBNode* link = arrayRes;
for(int i = 0; i < stackSize; i++){
link = link->childAt(stack.at(i).second);
}
link = new DBNode(curArrDataItem, link);
stack.push_back(QPair<NodeData, int>(curArrDataItem, link->getParent()->childCount() - 1));
}
}