gistfile1.rb

def solution(strengths, weights, connections)    
    # simulate the order by going through the conections and building the graph
    # at each step, evaluate the graph to detect breaks
    # at each step, attach the weight, then travel up the graph and check for breaks O(n * log(n))
    
    # data structure:
    # node(parent_node, strength, weight (incl. children), children)
    # map(i: node)
    
    # create root node
    map = {}
    count = 0
    
    # at each step:
    # get parent node
    # create new node and attach
    # start with new node weight, travel up parent, check whether strength < weight + added_weight
    connections.each_with_index do |parent_index, i|
        parent = map[parent_index]
        node = Node.new(weights[i], strengths[i],  parent)
        map[i] = node
       
        if parent
            parent.add_weight(node.weight)
        end
       
        if node.valid?
            count += 1
        else
            return count
        end
    end
    
    count
end

class Node
    attr_reader :parent, :strength, :weight
    
    def initialize(weight, strength, parent)
      @weight = weight
      @strength = strength
      @parent = parent
      @children = []
    end
    
    def add_weight(weight)
      @weight += weight
      
      if parent
         parent.add_weight(weight) 
      end
    end
    
    def valid?
        weight <= strength && (parent.nil? || parent.valid?)
    end
end