Grokking Tree Coding Patterns for Interviews
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Count Good Nodes in Binary Tree (medium)
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Problem Statement

Given a binary tree root, return the number of good nodes in the binary tree.

A node is considered good if in the path from the root to this node, there are no nodes with a value greater than this node's value.

Examples

Example 1

  • Input: root = [3, 1, 3, 3, null, 1, 5]
Image
  • Expected Output: 4
  • Explanation:
    • Root node (3) is always good.
    • Node 5 is also a good node.
    • Both nodes 3 are good.

Example 2

  • Input: root = [2, 3, 4, 1, null, null, 5]
Image
  • Expected Output: 4
  • Explanation:
    • Nodes 2, 3, 4, and 5 are good.
    • The node with value 1 is not good because 3 is greater and comes before it.

Example 3

  • Input: root = [10, 8, 15, 7, 9, 12, 20]
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  • Expected Output: 3
  • Explanation:
    • Nodes 10, 15, and 20 are good.

Constraints:

  • The number of nodes in the binary tree is in the range [1, 10^<sup>5</sup>].
  • Each node's value is between [-10<sup>4</sup>, 10^<sup>4</sup>].

Try it yourself

Try solving this question here:

Python3
Python3
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