title: Merge two binary trie
body: <p>I want to merge two trie structures, but the best complexity I can think of is </p>
  
  <p>Get list of values from other trie: O(n), n is number of nodes in trie.
  Insert all values from list intro target trie: n * O(m), m is length of key
  Taking into account, that at worst, the key is of size n, isn't the complexity of merge O(n^2)? </p>
  
  <p>Is there any better way of doing it?</p>