solve : binary tree level order traversal

Author: SamTheKorean

binary-tree-level-order-traversal/samthekorean.py

@@ -0,0 +1,24 @@
+# TC : O(n)
+# SC : O(n)
+class Solution:
+    def levelOrder(self, root: Optional[TreeNode]) -> List[List[int]]:
+        q = collections.deque()
+        res = []
+        q.append(root)
+
+        while q:
+            level = []
+            qLen = len(q)
+
+            # traverse nodes in each level and append left and right subtree if node is None
+            for i in range(qLen):
+                node = q.popleft()
+                if node:
+                    level.append(node.val)
+                    # append the subtrees of q for the next level in advance
+                    q.append(node.left)
+                    q.append(node.right)
+            if level:
+                res.append(level)
+
+        return res