Leetcode skimming: binary tree 07 (maximum depth of binary tree)

104. The maximum depth of a binary tree

Force button topic link

Given a binary tree , Find out the maximum depth .

The depth of a binary tree is the number of nodes in the longest path from the root node to the farthest leaf node .

explain : A leaf node is a node that has no children .

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

Return to its maximum depth 3 .

I was stuck for a long time at first , Later it was the same , You can use hierarchical traversal to do , After each floor , Maximum depth + 1 that will do .