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.
Input: root = [3,1,4,3,null,1,5]
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.
Input: root = [3,3,null,4,2]
Explanation: Node 2 -> (3, 3, 2) is not good, because "3" is higher than it.
Input: root = 
Explanation: Root is considered as good.
- The number of nodes in the binary tree is in the range
- Each node’s value is between
Using depth-first search to find out all the nodes greater than X, if the nodes are greater, then add it into numOfGoodNodes.