# LeetCode — Count Good Nodes in Binary Trees

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: 4Explanation: 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 pathNode 3 -> (3,1,3) is the maximum value in the path.`

Example 2:

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

Example 3:

`Input: root = [1]Output: 1Explanation: 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]`.

Solution:

Using depth-first search to find out all the nodes greater than X, if the nodes are greater, then add it into numOfGoodNodes.

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Dell Technologies — VxRail Software Engineer 👨‍💻

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## Steven Lu

Dell Technologies — VxRail Software Engineer 👨‍💻