#!/usr/bin/env ruby -w

require 'yaml'

classes = {
    'english' => ['Andy', 'Bob', 'Charlie'],
    'math'    => ['Charlie', 'Paul', 'Frank'],
    'physics' => ['Bob', 'Thomas', 'Frank', 'Earl'],
    'cs'      => ['Thomas', 'Dennis', 'Richard'],
    'chem'    => ['Earl', 'Gordon']
}

graph = {}
classes.keys.each do |classname|
    graph[classname] = []
end

classes.each do |classname1, members1|
    classes.each do |classname2, members2|
        if classname1 < classname2
            intersection = members1 & members2
            unless intersection.empty?
                graph[classname1].push(classname2)
                graph[classname2].push(classname1)
            end
        end
    end
end

sets = []
nodes = graph.keys
while not nodes.empty?
    node = nodes.shift
    set = [node]
    nodes.each do |n|
        unless graph[n].include? node
            set.push n
            nodes.delete n
        end
    end
    sets.push(set)
end

sets.each do |set|
    puts "[#{set.sort.join(', ')}]"
end