Submission #1674545

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Source Code Expand

n, x = gets.chomp.split(" ").map(&:to_i)
node = Struct.new("Node", :to)
@h = [0] + gets.chomp.split(" ").map(&:to_i)
@g = Array.new(n+1){node.new([])}
(n-1).times do
  a, b = gets.chomp.split(" ").map(&:to_i)
  @g[a].to << b
  @g[b].to << a
end

@par = Array.new(n+1, -1)
cand = [x]
@par[x] = 0
while true
  break if cand.empty?
  v = cand.pop
  @g[v].to.each do |i|
    if @par[i] == -1
      @par[i] = v
      cand << i
    end
  end
end

def jewel?(v)
  if @h[v] == 1
    return true
  end
  @g[v].to.each do |i|
    next if i == @par[v]
    if @h[i] == 1
      return true
    else
      jewel?(i)
    end
  end
  return false
end


visited = Array.new(n+1, false)
visited[x] = true
cand = [x]
@cost = 0
while true
  break if cand.empty?
  v = cand.pop
  @g[v].to.each do |i|
    if !visited[i] && jewel?(i)
      cand << i
      @cost += 2
    end
    visited[i] = true
  end
end

puts @cost

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