Maximum Depth of Binary Tree A binary tree’s maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.
Example 1:


Input: root = [3,9,20,null,null,15,7] Output: 3
Example 2:
Input: root = [1,null,2] Output: 2
Constraints:
- The number of nodes in the tree is in the range
[0, 104]
. -100 <= Node.val <= 100
Maximum Depth of Binary Tree Solutions
✅Time: O(n)
✅Space: O(1)
C++
class Solution {
public:
int maxDepth(TreeNode* root) {
if (!root)
return 0;
return 1 + max(maxDepth(root->left), maxDepth(root->right));
}
};
Java
class Solution {
public int maxDepth(TreeNode root) {
if (root == null)
return 0;
return 1 + Math.max(maxDepth(root.left), maxDepth(root.right));
}
}
Python
class Solution:
def maxDepth(self, root: Optional[TreeNode]) -> int:
if not root:
return 0
return 1 + max(self.maxDepth(root.left), self.maxDepth(root.right))
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