goodNodes.py

'''
1448. Count Good Nodes in Binary Tree

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.

'''

def goodNodes(self, root: TreeNode) -> int:
  route = []
  count = 0
  stack = []
  while stack or root:
      while root:
          route = route+[root.val]
          stack.append((root, route))
          root = root.left
      root, route = stack.pop()
      if max(route) == route[-1]:
          count+=1
      root = root.right
  return count