// 104. 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.

// Runtime: 0 ms, faster than 100.00% of Java online submissions for Maximum Depth of Binary Tree.

// Memory Usage: 40.9 MB, less than 5.38% of Java online submissions for Maximum Depth of Binary Tree.

public class Solution {

/**

* Definition for a binary tree node.

* public class TreeNode {

* int val;

* TreeNode left;

* TreeNode right;

* TreeNode(int x) { val = x; }

* }

*/

public int maxDepth(TreeNode root) {

if (Objects.isNull(root)) {

return 0;

}

return Math.max(checkLeaf(root.left), checkLeaf(root.right));

}

private int checkLeaf(TreeNode root) {

if (Objects.isNull(root)) {

return 1;

}

return 1 + Math.max(checkLeaf(root.right), checkLeaf(root.left));

}

}