Binary tree in-order traversal solution

Author: joshguha

94_binary_tree_inorder_traversal.py

@@ -0,0 +1,79 @@
+# 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 inorderTraversal(self, root):
+    #     """
+    #     :type root: TreeNode
+    #     :rtype: List[int]
+    #     """
+    #     # recursively
+    #     res = []
+    #     self.do_inorderTraversal(res, root)
+    #     return res
+    #
+    # def do_inorderTraversal(self, res, curr):
+    #     if curr is None:
+    #         return
+    #     if curr.left is not None:
+    #         self.do_inorderTraversal(res, curr.left)
+    #     res.append(curr.val)
+    #     if curr.right is not None:
+    #         self.do_inorderTraversal(res, curr.right)
+
+    # def inorderTraversal(self, root):
+    #     # iteratively, but break the tree
+    #     res = []
+    #     if root is None:
+    #         return res
+    #     queue = [root]
+    #     while len(queue) > 0:
+    #         curr = queue.pop(0)
+    #         if curr.left is None and curr.right is None:
+    #             res.append(curr.val)
+    #         else:
+    #             if curr.right is not None:
+    #                 queue.insert(0, curr.right)
+    #                 curr.right = None
+    #             queue.insert(0, curr)
+    #             if curr.left is not None:
+    #                 queue.insert(0, curr.left)
+    #                 curr.left = None
+    #     return res
+    # def inorderTraversal(self, root):
+    #     res = []
+    #     stack = []
+    #     while root is not None:
+    #         stack.append(root)
+    #         root = root.left
+    #         while root is None:
+    #             if len(stack) == 0:
+    #                 return res
+    #             root = stack.pop()
+    #             res.append(root.val)
+    #             root = root.right
+    #     return res
+
+    def inorderTraversal(self, root):
+        if root is None:
+            return []
+        res = []
+        stack = [root]
+        while len(stack) > 0:
+            curr = stack.pop()
+            if not isinstance(curr, TreeNode):
+                res.append(curr)
+                continue
+            if curr.right is not None:
+                stack.append(curr.right)
+            stack.append(curr.val)
+            if curr.left is not None:
+                stack.append(curr.left)
+        return res
+
+
+