543. 二叉树的直径

class Solution {
  int Diameter{};
  int Traverse(TreeNode *root) {
    if (!root)
      return 0;
    int DiaL = 0, DiaR = 0;
    if (root->left)
      DiaL = Traverse(root->left) + 1;
    if (root->right)
      DiaR = Traverse(root->right) + 1;
    Diameter = std::max(Diameter, DiaL + DiaR);
    return std::max(DiaL, DiaR);
  }

public:
  int diameterOfBinaryTree(TreeNode* root) {
    Traverse(root);
    return Diameter;
  }
};

class Solution {
  int Diameter_{};
  int LocalDepth(TreeNode *root) {
    if (!root)
      return 0;
    int LDepth = LocalDepth(root->left);
    int RDepth = LocalDepth(root->right);
    Diameter_ = max(Diameter_, LDepth + RDepth);
    return max(LDepth, RDepth) + 1;
  }
public:
  int diameterOfBinaryTree(TreeNode* root) {
    LocalDepth(root);
    return Diameter_;
  }
};