From: Rick DeNatale <rick.denatale@...>
Date: 2006-09-11T00:25:11+09:00
Subject: Re: Puzzling bug with yielded array

On 9/9/06, A. S. Bradbury <asbradbury@tekcentral.org> wrote:

> I can see other forms of tree traversal lending themselves well to a recursive
> implementation, but not really level by level, particular as I want each
> level to be returned as an array.

Here's a recursive implementation of that then:

        def each_level(include_self=false, levels=[[]], depth=0)
                levels[depth] << self if include_self
                kids = self.children.values
                unless kids.empty?
                        levels << [] unless levels.length > depth + 1
                        kids.each {|kid| kid.each_level(true, levels, depth+1)}
                end
                levels.each {|l| yield l} if depth.zero?
        end

Although it might be better to make a public wrapper method to start,
and make the internal recursive method private, so as not to expose
the extra parameters:

        def each_level(include_self=false)
                levels = []
                levels << [self] if include_self
                kids = self.children.values
                unless kids.empty?
                        levels << []
                        kids.each {|kid| kid.each_level_internal(levels, 1)}
                end
                levels.each {|l| yield l}
        end

        private
        def each_level_internal(levels, depth)
                levels[depth] << self
                kids = self.children.values
                unless kids.empty?
                        levels << [] unless levels.length > depth + 1
                        kids.each {|kid|
kid.each_level_internal(levels, depth+1)}
                end
        end


-- 
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/