輸入一棵二叉樹，求該樹的深度。從根結(jié)點(diǎn)到葉結(jié)點(diǎn)依次經(jīng)過的結(jié)點(diǎn)（含根、葉結(jié)點(diǎn)）形成樹的一條路徑，最長路徑的長度為樹的深度。

IDEA

DFS遍歷，左右遞歸返回左右子樹最長的

CODE

/**public class TreeNode {    int val = 0;    TreeNode left = null;    TreeNode right = null;    public TreeNode(int val) {        this.val = val;    }}*/public class Solution {    public int TreeDepth(TreeNode root) {        if(root==null){            return 0;        }        int num_left=TreeDepth(root.left);        int num_right=TreeDepth(root.right);        return num_left>num_right?(num_left+1):(num_right+1);    }}