Created
October 14, 2011 23:23
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class State | |
attr_accessor :value, :parent, :cost, :distance | |
def initialize(value, distance, parent) | |
@value, @distance, @parent, @cost = value, distance, parent, 0 | |
end | |
def to_s; value; end | |
end | |
def search(strategy, current, final) | |
return false if current.nil? | |
return true if current.value == final | |
strategy.produce(current) | |
search(strategy, strategy.choice, final) | |
end | |
# Best-first | |
class BestFirstStrategy < Array | |
attr_reader :visited | |
def initialize(state_space) | |
@state_space = state_space | |
@visited = [] | |
end | |
def produce(state) | |
@state_space.each do |current_state| | |
if current_state.parent == state.value | |
current_state.cost = current_state.distance + state.cost | |
push(current_state) | |
end | |
end | |
end | |
def choice | |
node = min_by{ |n| n.cost }; | |
delete_if{ |n| n.value == node.value } | |
@visited.push(node) unless node.nil? | |
node | |
end | |
end | |
# state space | |
ss = [] | |
ss << State.new(:arad, 0, nil) | |
ss << State.new(:zerind, 75, :arad) | |
ss << State.new(:timisoara, 118, :arad) | |
ss << State.new(:sibiu, 140, :arad) | |
ss << State.new(:oradea, 71, :zerind) | |
ss << State.new(:sibiu, 151, :oradea) | |
ss << State.new(:fagaras, 99, :sibiu) | |
ss << State.new(:rimnicu, 80, :sibiu) | |
ss << State.new(:bucharest, 211, :fagaras) | |
ss << State.new(:pitesti, 97, :rimnicu) | |
def find_parent(ss, value) | |
ss.select do |s| | |
s.value == value | |
end.first | |
end | |
strategy = BestFirstStrategy.new(ss) | |
puts "Found? #{search(strategy, ss.first, :bucharest)}" | |
goal = strategy.visited.select{ |s| s.value == :bucharest }.first | |
puts goal | |
s = goal | |
while s != nil | |
p s.value | |
s = find_parent(ss, s.parent) | |
end | |
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