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LeetCode 104 Maximum Depth Of Binary Tree - Easy

104. Maximum Depth of Binary Tree

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104. Maximum Depth Of Binary Tree — Easy

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Problem

  1. Maximum Depth of Binary Tree

Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

Note: A leaf is a node with no children.

Example:

Given binary tree [3,9,20,null,null,15,7],

3

/
9 20 /
15 7 return its depth = 3.

Solution

### 分治法 + DFS + Recursion：
 
# 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 maxDepth(self, root):
        max_depth = self.dfs(root)
        return max_depth
    
    def dfs(self, root):
        if not root:
            return 0
        
        left_depth = self.dfs(root.left)
        right_depth = self.dfs(root.right)
        height = max(left_depth, right_depth) + 1
        return height

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