adding algo

src/my_project/interviews/google_top_exercises/round_1/18_binary_tree_level_order_traversal.py

@@ -0,0 +1,31 @@
+from typing import Optional, List 
+from collections import deque
+
+class TreeNode:
+    def __init__(self, val=0, left=None, right=None):
+        self.val = val
+        self.left = left
+        self.right = right
+
+class Solution:
+    def levelOrder(self, root: Optional[TreeNode]) -> List[List[int]]:
+
+        if not root: 
+            return []
+
+        answer = list()
+        queue = deque([root])
+
+        while queue: 
+            level_size = len(queue)
+            level = []
+            for _ in range(level_size):
+                node = queue.popleft()
+                level.append(node.val)
+                if node.left:
+                    queue.append(node.left)
+                if node.right:
+                    queue.append(node.right)
+            answer.append(level)                
+
+        return answer