/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    int maxres=0;
    int diameterOfBinaryTree(TreeNode* root) {
        int high=hight(root);
        return maxres;
    }
    int hight(TreeNode* root)
    {
        if(root==nullptr)
        {
            return 0;
        }
        int left_h=hight(root->left);
        int right_h=hight(root->right);
        //应该是在递归求以每个节点作为根时树的深度时的最大值 因为不一定就是以root为根时结果会最大
        maxres=max(maxres,left_h+right_h);
        return max(left_h,right_h)+1;
    }
};