// Time:  O(n)
// Space: O(w)

class Solution {
public:
    TreeNode* findNeartestRightNode(TreeNode* root, TreeNode* u) {
        vector<TreeNode *> q = {root};
        while (!empty(q)) {
            vector<TreeNode *> new_q;
            for (int i = 0; i < size(q); ++i) {
                if (q[i] == u) {
                    return i + 1 < size(q) ? q[i + 1] : nullptr;
                }
                if (q[i]->left) {
                    new_q.emplace_back(q[i]->left);
                }
                if (q[i]->right) {
                    new_q.emplace_back(q[i]->right);
                }
            }
            q = move(new_q);
        }
        return nullptr;
    }
};