9.23

Author: huangyt39

66.py

@@ -0,0 +1,32 @@
+"""
+Definition of TreeNode:
+"""
+class TreeNode:
+    def __init__(self, val):
+        self.val = val
+        self.left, self.right = None, None
+
+class Solution:
+    """
+    @param root: A Tree
+    @return: Preorder in ArrayList which contains node values.
+    """
+    def preorderTraversal(self, root):
+        if root == None:
+          return []
+        # write your code here
+        arr = []
+        stack = []
+        stack.append(root)
+        tmp = root
+        while len(stack) != 0:
+          tmp = stack[-1]
+          arr.append(tmp.val)
+          stack.pop()
+          if tmp.right:
+            stack.append(tmp.right)
+          if tmp.left:
+            stack.append(tmp.left)
+        return arr
+
+

95.py

@@ -0,0 +1,31 @@
+ """
+Definition of TreeNode:
+"""
+class TreeNode:
+    def __init__(self, val):
+        self.val = val
+        self.left, self.right = None, None
+
+class Solution:
+    """
+    @param root: The root of binary tree.
+    @return: True if the binary tree is BST, or false
+    """
+    def isValidBST(self, root):
+        # write your code here
+        if root == None:
+          return True
+        res = []
+        res = Solution.midTraverse(root, root, res)
+        for i in range(len(res) - 1):
+          if res[i] >= res[i + 1]:
+            return False
+        return True
+        
+    def midTraverse(self, root, res_arr):
+      if root == None:
+        return res_arr
+      res_arr = Solution.midTraverse(root, root.left, res_arr)
+      res_arr.append(root.val)
+      res_arr = Solution.midTraverse(root, root.right, res_arr)
+      return res_arr