class Solution {
public:
    bool isTarget = false;
    TreeNode* inorderSuccessor(TreeNode* root, TreeNode* p) {
        if(root == nullptr) return nullptr;
        
        TreeNode* left = inorderSuccessor(root->left, p);
        if(left != nullptr) return left;

        if(isTarget){
            return root;
        }
        if(p->val == root->val){
            isTarget = true;
        }
        TreeNode* right = inorderSuccessor(root->right, p);
        if(right != nullptr) return right;
        return nullptr;
    }
};

class Solution {
public:
    TreeNode* inorderSuccessor(TreeNode* root, TreeNode* p) {
        TreeNode* sucessor = nullptr;

        while(root != nullptr){
            if(root->val <= p->val){
                root = root->right;
            } else {
                sucessor = root;
                root = root->left;
            }
        }

        return sucessor;
    }
};