[Feature] Level-Order traversal for naive trees.

Author: exterkamp

README.md

@@ -46,6 +46,7 @@ $ coverage report -m
   * [In-Order Traversal](structures/naive_tree.py)
   * [Pre-Order Traversal](structures/naive_tree.py)
   * [Post-Order Traversal](structures/naive_tree.py)
+  * [Level-Order Traversal](structures/naive_tree.py)
 * [Binary Search Tree](structures/binary_search_tree.py)
 * [Hash Map](structures/hash_map.py)
   * [DJB2 Hash Function](structures/hash_map.py)

structures/naive_tree.py

@@ -1,3 +1,5 @@
+from collections import deque
+
 class NaiveBinaryTree():
 
     def __init__(self):
@@ -40,3 +42,19 @@ def recur(node):
                 output.append(node.value)
         recur(self.head)
         return output
+
+    def level_order_traversal(self):
+        output = []
+        queue = deque([self.head])
+
+        while queue:
+            output.extend(list(map(lambda n: n.value, list(queue))))
+            next_level = deque()
+            while queue:
+                current = queue.popleft()
+                if current.left:
+                    next_level.append(current.left)
+                if current.right:
+                    next_level.append(current.right)
+            queue = next_level
+        return output

tests/test_tree.py

@@ -63,6 +63,16 @@ def test_post_order_traversal(self):
 
         self.assertEqual([17,8,3,2,6,12], tree.post_order_traversal())
 
+    def test_level_oreder_traversal(self):
+
+        tree = self.make_simple_tree()
+
+        self.assertEqual([3, 5, 7], tree.level_order_traversal())
+
+        tree = self.make_complex_tree()
+
+        self.assertEqual([12,3,6,8,2,17], tree.level_order_traversal())
+
     def test_print(self):
 
         tree = self.make_simple_tree()