998. Maximum Binary Tree II

Medium

A maximum tree is a tree where every node has a value greater than any other value in its subtree.

You are given the root of a maximum binary tree and an integer val.

Just as in the previous problem, the given tree was constructed from a 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 the 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]

Constraints:

• The number of nodes in the tree is in the range [1, 100].

• 1 <= Node.val <= 100

• All the values of the tree are unique.

• 1 <= val <= 100

解題

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func insertIntoMaxTree(root *TreeNode, val int) *TreeNode {
    if root == nil {
        return &TreeNode{ Val:val }
    }

    if val > root.Val {
        newnode := &TreeNode { Val:val, Left: root}
        return newnode
    }

    root.Right = insertIntoMaxTree(root.Right, val)

    return root
}