力扣第543题 二叉树的直径

力扣第543题 二叉树的直径

/**
 * Definition for a binary tree node.

 * struct TreeNode {

 * int val;

 * TreeNode *left;

 * TreeNode *right;

 * TreeNode(int x) : val(x), left(NULL), right(NULL) {}

 * };
   */
   class Solution {
   public:
   int res;
   int func(TreeNode* root)
   {
       if (root == NULL)
           return 0;
       int left = func(root->left);
       int right = func(root->right);
       res = max<int>(res, left + right + 1);
       return max<int>(left, right) + 1;
   }

   int diameterOfBinaryTree(TreeNode* root)
   {
       res = 1;
       func(root);
       return res - 1;
   }
};