add merge function for trie

data_structures/trie/trie.py

@@ -4,6 +4,7 @@
 making it impractical in practice. It however provides O(max(search_string, length of
 longest word)) lookup time making it an optimal approach when space is not an issue.
 """
+from __future__ import annotations
 
 
 class TrieNode:
@@ -33,6 +34,21 @@ def insert(self, word: str) -> None:
             curr = curr.nodes[char]
         curr.is_leaf = True
 
+    def merge(self, trie_node: TrieNode) -> None:
+        """
+        Merge the current instance of TrieNode with the passed instance.
+        :param trie_node: the source to be merged.
+        """
+
+        for source_node in trie_node.nodes:
+            if source_node not in self.nodes:
+                self.nodes[source_node] = TrieNode()
+
+            self.nodes[source_node].merge(trie_node.nodes[source_node])
+
+        if trie_node.is_leaf:
+            self.is_leaf = True
+
     def find(self, word: str) -> bool:
         """
         Tries to find word in a Trie
@@ -105,6 +121,16 @@ def test_trie() -> bool:
     root.delete("banana")
     assert not root.find("banana")
     assert root.find("bananas")
+
+    assert not root.find("new_merged_word")
+    assert not root.find("new_merged_word2")
+    node_to_merge = TrieNode()
+    node_to_merge.insert_many(["new_merged_word", "new_merged_word2"])
+    root.merge(node_to_merge)
+    assert root.find("new_merged_word")
+    assert root.find("new_merged_word2")
+    assert root.find("bananas")
+
     return True