题解 | #从上往下打印二叉树#

class Solution {
  public:
    std::vector<int> PrintFromTopToBottom(TreeNode* root) {
        std::vector<int> result;
        if (root == nullptr) {
            return result;
        }

        std::queue<TreeNode*> q;
        q.push(root);

        while (!q.empty()) {
            TreeNode* current = q.front();
            q.pop();
            result.push_back(current->val);

            if (current->left != nullptr) {
                q.push(current->left);
            }
            if (current->right != nullptr) {
                q.push(current->right);
            }
        }

        return result;
    }
};