直接递归即可
class Solution {
public int maxDepth(TreeNode root) {
if(root==null) return 0;
int left=maxDepth(root.left);
int right=maxDepth(root.right);
return Math.max(left,right)+1;
}
}

直接递归即可
class Solution {
public int maxDepth(TreeNode root) {
if(root==null) return 0;
int left=maxDepth(root.left);
int right=maxDepth(root.right);
return Math.max(left,right)+1;
}
}