104. Maximum Depth of Binary Tree
题目链接
104. Maximum Depth of Binary Tree
题目分析
返回给定的二叉树有多少层。
思路
每下一级,层树 +1,并记录到类属性 level 中。并判断是否大于已知最深层树。
最终代码
<?php
/**
* Definition for a binary tree node.
* class TreeNode {
* public $val = null;
* public $left = null;
* public $right = null;
* function __construct($value) {$this->val = $value;}
* }
*/
class Solution {
public $max = 0;
public $level = 0;
/**
* @param TreeNode $root
* @return Integer
*/
function maxDepth($root) {if($root){$this->level++;}
if($this->level>=$this->max){$this->max = $this->level;}
if($root->left){$this->maxDepth($root->left);
}
if($root->right){$this->maxDepth($root->right);
}
$this->level--;
return $this->max;
}
}
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