Create maximum-sum-bst-in-binary-tree.py

Author: kamyu104

Python/maximum-sum-bst-in-binary-tree.py

@@ -0,0 +1,31 @@
+# Time:  O(n)
+# Space: O(h)
+
+# 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 maxSumBST(self, root):
+        """
+        :type root: TreeNode
+        :rtype: int
+        """
+        def dfs(node, result):
+            if not node:
+                return True, 0, float("inf"), float("-inf")
+            lvalid, lsum, lmin, lmax = dfs(node.left, result)
+            rvalid, rsum, rmin, rmax = dfs(node.right, result)
+            if lvalid and rvalid and lmax < node.val < rmin:
+                total = lsum + node.val + rsum
+                result[0] = max(result[0], total)
+                return True, total, min(lmin, node.val), max(node.val, rmax)
+            return False, 0, 0, 0
+
+        result = [0]
+        dfs(root, result)
+        return result[0]