#include "s0098_validate_binary_search_tree.hpp"

struct TreeNodeState_S0098 {
  int maxVal;
  int minVal;
  bool isValidBST;
};

TreeNodeState_S0098 isValidBSTHelper(TreeNode* root) {
  if (root == nullptr) return TreeNodeState_S0098{0, 0, false};
  if (root->left == nullptr && root->right != nullptr) {
    TreeNodeState_S0098 rightState = isValidBSTHelper(root->right);
    return TreeNodeState_S0098{
        rightState.maxVal, root->val,
        root->val < rightState.minVal && rightState.isValidBST};
  } else if (root->left != nullptr && root->right == nullptr) {
    TreeNodeState_S0098 leftState = isValidBSTHelper(root->left);
    return TreeNodeState_S0098{
        root->val, leftState.minVal,
        root->val > leftState.maxVal && leftState.isValidBST};
  } else if (root->left != nullptr && root->right != nullptr) {
    TreeNodeState_S0098 leftState = isValidBSTHelper(root->left);
    TreeNodeState_S0098 rightState = isValidBSTHelper(root->right);
    return TreeNodeState_S0098{
        rightState.maxVal, leftState.minVal,
        root->val > leftState.maxVal && root->val < rightState.minVal &&
            leftState.isValidBST && rightState.isValidBST};
  } else {
    return TreeNodeState_S0098{root->val, root->val, true};
  }
}

bool S0098::isValidBST(TreeNode* root) {
  return isValidBSTHelper(root).isValidBST;
}