998 Maximum Binary Tree II.py

Author: rajeevranjancom

998 Maximum Binary Tree II.py

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+#!/usr/bin/python3
+"""
+We are given the root node of a maximum tree: a tree where every node has a
+value greater than any other value in its subtree.
+
+Just as in the previous problem, the given tree was constructed from an list A
+(root = Construct(A)) recursively with the following Construct(A) routine:
+
+If A is empty, return null.
+Otherwise, let A[i] be the largest element of A.  Create a root node with value
+A[i].
+The left child of root will be Construct([A[0], A[1], ..., A[i-1]])
+The right child of root will be Construct([A[i+1], A[i+2], ...,
+A[A.length - 1]])
+Return root.
+Note that we were not given A directly, only a root node root = Construct(A).
+
+Suppose B is a copy of A with the value val appended to it.  It is guaranteed
+that B has unique values.
+
+Return Construct(B).
+
+Example 1:
+Input: root = [4,1,3,null,null,2], val = 5
+Output: [5,4,null,1,3,null,null,2]
+Explanation: A = [1,4,2,3], B = [1,4,2,3,5]
+
+Example 2:
+Input: root = [5,2,4,null,1], val = 3
+Output: [5,2,4,null,1,null,3]
+Explanation: A = [2,1,5,4], B = [2,1,5,4,3]
+
+Example 3:
+Input: root = [5,2,3,null,1], val = 4
+Output: [5,2,4,null,1,3]
+Explanation: A = [2,1,5,3], B = [2,1,5,3,4]
+"""
+
+
+# Definition for a binary tree node.
+class TreeNode:
+    def __init__(self, x):
+        self.val = x
+        self.left = None
+        self.right = None
+
+
+class Solution:
+    def insertIntoMaxTree(self, root: TreeNode, val: int) -> TreeNode:
+        """
+        Suppose B is a copy of A with the value val appended to it.
+        val is ALWAYS on the right
+
+        insert the node in the root
+        Go through the example one by one.
+        Need to maintain the parent relationship -> return the sub-root
+        """
+        if not root:
+            return TreeNode(val)
+
+        if val > root.val:
+            node = TreeNode(val)
+            node.left = root
+            return node
+
+        root.right = self.insertIntoMaxTree(root.right, val)
+        return root