[Feature] Added basic Trie data structure.

Author: exterkamp

README.md

@@ -43,6 +43,7 @@ $ coverage report -m
   * [SDBM Hash Function](structures/hash_map.py)
   * [Lose/Lose Hash Function](structures/hash_map.py)
 * [Heap](structures/heap.py)
+* [Trie](structures/trie.py)
 
 ### Algorithms
 

structures/trie.py

@@ -0,0 +1,17 @@
+class Trie():
+
+    eof = '__eof__'
+
+    def __init__(self, words):
+        self.head = {}
+        for word in words:
+            current = self.head
+            for letter in word:
+                current = current.setdefault(letter, {})
+            current[self.eof] = self.eof
+    
+    def add(self, word):
+        current = self.head
+        for letter in word:
+            current = current.setdefault(letter, {})
+        current[self.eof] = self.eof

tests/test_trie.py

@@ -0,0 +1,21 @@
+import unittest
+from structures.trie import Trie
+
+class TestTrie(unittest.TestCase):
+
+    def test_trie(self):
+        trie = Trie(['hello','hel','headway','tree','second','true'])
+
+        self.assertTrue(Trie.eof in trie.head['h']['e']['l'])
+        self.assertTrue(Trie.eof in trie.head['t']['r']['e']['e'])
+        self.assertTrue(Trie.eof in trie.head['h']['e']['l']['l']['o'])
+    
+    def test_add(self):
+        trie = Trie(['1',])
+
+        with self.assertRaises(KeyError):
+            trie.head['2']
+
+        trie.add('2')
+
+        self.assertTrue(Trie.eof in trie.head['2'])