Loop-free many-to-many (bitcoin) accounting in Ruby

xfer.rb

#!/usr/bin/ruby

tx = {
  "inputs" => [
    {
      "address" => "abc",
      "value" => 6
    },
    {
      "address" => "def",
      "value" => 4
    },
    {
      "address" => "ghi",
      "value" => 3
    }
  ],
  "outputs" => [
    {
      "address" => "jkl",
      "value" => 2
    },
    {
      "address" => "mno",
      "value" => 2
    },
    {
      "address" => "pqr",
      "value" => 1
    }
  ]
}

my_wallet = [ "abc", "mno", "xyz" ]

inbound = tx["outputs"]
  .select { |index| my_wallet.include?(index["address"]) }
  .map { |pair| pair["value"] }
  .reduce(:+)

outbound = tx["inputs"]
  .select { |index| my_wallet.include?(index["address"]) }
  .map { |pair| pair["value"] }
  .reduce(:+)

xfer = inbound - outbound

puts xfer.to_s