LeetCode-in-All
104. Maximum Depth of Binary Tree
Easy
Given the root of a binary tree, return its maximum depth.
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
Example 3:
Input: root = []
Output: 0
Example 4:
Input: root = [0]
Output: 1
Constraints:
- The number of nodes in the tree is in the range
[0, 104]. -100 <= Node.val <= 100
Solution
/**
* Definition for a binary tree node.
* class TreeNode {
* public $val = null;
* public $left = null;
* public $right = null;
* function __construct($val = 0, $left = null, $right = null) {
* $this->val = $val;
* $this->left = $left;
* $this->right = $right;
* }
* }
*/
class Solution {
/**
* @param TreeNode $root
* @return Integer
*/
function maxDepth($root) {
return $this->findDepth($root, 0);
}
private function findDepth($node, $currentDepth) {
if ($node == null) {
return 0;
}
$currentDepth++;
return 1
+ max($this->findDepth($node->left, $currentDepth), $this->findDepth($node->right, $currentDepth));
}
}