Create MaximumSumBSTInBinaryTree.py

Author: DreamOfTheRedChamber

Python/Tree/MaximumSumBSTInBinaryTree.py

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+# Definition for a binary tree node.
+import heapq
+import sys
+import unittest
+
+# Read about enumerate in python
+from collections import defaultdict
+from typing import List
+
+class TreeNode:
+    def __init__(self, val=0, left=None, right=None):
+        self.val = val
+        self.left = left
+        self.right = right
+
+class MaximumSumBstInBinaryTree(unittest.TestCase):
+
+    def maxSumBST2(self, root: TreeNode) -> int:
+        # returns {lo, hi, sum, valid}
+        def dfs(node):
+            if not node: return (1e9, -1e9, 0, True)
+            ll, lh, ls, lv = dfs(node.left)
+            rl, rh, rs, rv = dfs(node.right)
+            v = lv and rv and node.val > lh and node.val < rl
+            s = ls + rs + node.val if v else -1
+            self.ans = max(self.ans, s)
+            return (min(ll, node.val), max(rh, node.val), s, v)
+
+        self.ans = 0
+        dfs(root)
+        return self.ans
+
+    def maxSumBST(self, root: TreeNode) -> int:
+        def helper(node: TreeNode) -> (bool, int, int, int):  # isBST, sum, maxValue, minValue
+            if not node:
+                return True, 0, -1e9, 1e9
+
+            isBSTLeft, leftSum, leftMaxValue, leftMinValue = helper(node.left)
+            isBSTRight, rightSum, rightMaxValue, rightMinValue = helper(node.right)
+
+            isBST = isBSTLeft and isBSTRight and leftMaxValue < root.val < rightMinValue
+            sumValue = leftSum + rightSum + node.val if isBST else -1
+            maxValue = max(leftMaxValue, rightMaxValue, node.val)
+            minValue = min(leftMinValue, rightMinValue, node.val)
+            self.ans = max(self.ans, sumValue)
+            return isBST, sumValue, maxValue, minValue
+
+        self.ans = 0
+        isBST, sumValue, maxValue, minValue = helper(root)
+        return self.ans
+
+    def test_Leetcode(self):
+        node1 = TreeNode(5)
+        node2 = TreeNode(4)
+        node3 = TreeNode(8)
+        node4 = TreeNode(3)
+        node5 = TreeNode(6)
+        node6 = TreeNode(3)
+        node1.left = node2
+        node1.right = node3
+        node2.left = node4
+        node2.right = None
+        node3.left = node5
+        node3.right = node6
+        self.assertEqual(7, self.maxSumBST(node1))
+
+if __name__ == '__main__':
+    unittest.main()