[2022][ruby][16.1]

2022/ruby/day_16.rb

@@ -0,0 +1,89 @@
+require "set"
+
+Valve = Data.define(:name, :flow_rate, :tunnels)
+
+valves = ARGF.read.scan(/Valve (.+) has flow rate=(\d+); tunnels? leads? to valves? ((?~\n))/)
+  .map {|name, flow_rate, tunnels|
+    Valve.new(name, flow_rate.to_i, tunnels.split(", "))
+  }
+
+Network = Data.define(:valves) do
+  def initialize(*)
+    @connections = Hash.new {|h,start|
+      current = [[start]]
+      result = { start => %w[ AA ] }
+
+      until current.empty?
+        path = current.shift
+        links = valves.fetch(path.last).tunnels
+          .reject { result.has_key?(_1) }
+          .map { path + [_1] }
+        result.merge!(links.to_h { [_1.last, _1] })
+        current.concat(links)
+      end
+
+      h[start] = result
+    }
+
+    super
+  end
+
+  def connections(start) = @connections[start]
+end
+
+Move = Data.define(:reward, :target, :path) do
+  def cost = path.length
+end
+
+State = Data.define(:net, :current, :max, :turn, :pressure, :opened) do
+  def best_moves
+    best_moves = []
+    best_state = self
+
+    moves.each do |move|
+      next_state = applied(move)
+      next_state, next_moves = next_state.best_moves;
+      next_moves << move
+      if next_state.pressure > best_state.pressure
+        best_moves = next_moves
+        best_state = next_state
+      end
+    end
+
+    [best_state, best_moves]
+  end
+
+  def applied(move)
+    self.class.new(
+      net,
+      move.target,
+      max,
+      turn + move.cost,
+      pressure + move.reward,
+      opened + [move.target],
+    )
+  end
+
+  def moves
+    return enum_for(__method__) unless block_given?
+
+    net
+      .connections(current)
+      .reject { opened.include?(_1) }
+      .each do |name, path|
+        flow = net.valves.fetch(name).flow_rate
+        reward = flow * (turns_left - path.length)
+        if reward.positive?
+          yield Move.new(reward, name, path)
+        end
+      end
+  end
+
+  def turns_left = max - turn
+end
+
+network = Network.new(valves.to_h { [_1.name, _1] })
+
+state = State.new(network, "AA", 30, 0, 0, [])
+best_state, moves = state.best_moves
+pp best_state, moves