给定一棵二叉树，采用广度优先搜索 (BFS) 算法，返回右视图所有节点的值。其中右视图定义为：二叉树的右视图是从树的右侧看过去时可见的节点集合，即右视图中的每个节点都是某一层中最右侧的节点。

struct TreeNode {
    int val;
    TreeNode* left;
    TreeNode* right;
    TreeNode(int x): val(x), left(nullptr), right(nullptr) {}
};

vector<int> rightSideView(TreeNode* root) {
    unordered_map<int, int> rightmostValueAtDepth;
    int max_depth = -1;

    queue<TreeNode*> nodeQueue;
    queue<int> depthQueue;
    nodeQueue.push(root);
    depthQueue.push(0);

    while (!nodeQueue.empty()) {
        TreeNode* node = nodeQueue.front(); nodeQueue.pop();
        int depth = depthQueue.front(); depthQueue.pop();

        if (node != NULL) {
            max_depth = max(max_depth, depth);

            rightmostValueAtDepth[depth] = node->val;

            nodeQueue.push(node->left);
            nodeQueue.push(node->right);

            depthQueue.push(________);
            depthQueue.push(________);
        }
    }

    vector<int> rightView;
    for (int depth = 0; ________; ++depth) {
        rightView.push_back(rightmostValueAtDepth[depth]);
    }
    return rightView;
};

{{ select(1) }}

• depth / depth / depth < max_depth
• depth + 1 / depth + 1 / depth <= max_depth
• depth + 1 / depth + 1 / depth < max_depth
• depth / depth / depth <= max_depth