1448. Count Good Nodes in Binary Tree

https://leetcode.com/problems/count-good-nodes-in-binary-tree

Description

Given a binary tree root, a node X in the tree is named good if in the path from root to X there are no nodes with a value greater than X.

Return the number of good nodes in the binary tree.

Example 1:

**Input:** root = [3,1,4,3,null,1,5]
**Output:** 4
**Explanation:** Nodes in blue are **good**.
Root Node (3) is always a good node.
Node 4 -> (3,4) is the maximum value in the path starting from the root.
Node 5 -> (3,4,5) is the maximum value in the path
Node 3 -> (3,1,3) is the maximum value in the path.

Example 2:

**Input:** root = [3,3,null,4,2]
**Output:** 3
**Explanation:** Node 2 -> (3, 3, 2) is not good, because "3" is higher than it.

Example 3:

**Input:** root = [1]
**Output:** 1
**Explanation:** Root is considered as **good**.

Constraints:

• The number of nodes in the binary tree is in the range [1, 10^5].

• Each node's value is between [-10^4, 10^4].

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