Create Binary Tree Preorder Traversal.py

Author: sugia

Binary Tree Preorder Traversal.py

@@ -0,0 +1,32 @@
+'''
+Given a binary tree, return the preorder traversal of its nodes' values.
+
+Example:
+
+Input: [1,null,2,3]
+   1
+    \
+     2
+    /
+   3
+
+Output: [1,2,3]
+'''
+
+# Definition for a binary tree node.
+# class TreeNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution(object):
+    def preorderTraversal(self, root):
+        """
+        :type root: TreeNode
+        :rtype: List[int]
+        """
+        if not root:
+            return []
+        
+        return [root.val] + self.preorderTraversal(root.left) + self.preorderTraversal(root.right)