diff --git a/work/1/Medium/Tree/1448.count-good-nodes-in-binary-tree.py b/work/1/Medium/Tree/1448.count-good-nodes-in-binary-tree.py new file mode 100644 index 0000000..1ee666a --- /dev/null +++ b/work/1/Medium/Tree/1448.count-good-nodes-in-binary-tree.py @@ -0,0 +1,94 @@ +""" +1448. Count Good Nodes in Binary Tree +Difficulty: Medium +https://leetcode.com/problems/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. + + + + +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]. +""" + + +# Definition for a binary tree node. +# class TreeNode: +# def __init__(self, val=0, left=None, right=None): +# self.val = val +# self.left = left +# self.right = right +class Solution: + def goodNodes(self, root: TreeNode) -> int: + def dfs(node, max_val): + if not node: + return 0 + + is_good = 1 if node.val >= max_val else 0 + new_max = max(max_val, node.val) + + return is_good + dfs(node.left, new_max) + dfs(node.right, new_max) + + return dfs(root, root.val)