adding useful code section

hws/08_youtube_comments/README.md

@@ -52,7 +52,7 @@ To summerize what your program does: your program reads all existing comments fr
 
 ## Format of input1.json
 
-input1.json represents the json files, it stores all existing comments. Each line of the .json file has this same format:
+input1.json represents the json files, it stores all existing comments. Each line of the .json file represents one comment, and each line has this same format:
 
 ```console
 {"video_id": "PMootRNTC-A", "author": "@tedybossu98", "comment_id": "UgwRfodAvGV1UOSQHhN4AaABAg", "like_count": 145, "reply_count": 51, "is_reply": false, "parent_comment_id": "", "published_date": "11 years ago", "crawled_date": "2023-10-31T22:35:37.499265", "is_video_owner": false, "comment": "Great Lord. Every time i hear this song i picture myself calling my ex and having the most romantic conversation on Earth. (her crying ..me crying) but when the song ends i never call her. I go play MW3 ..lame"}
@@ -204,6 +204,41 @@ Just like youtube, we use indentations to display the tree structure of the comm
 
 In this assignment, we define that a child comment should be indented by four space characters relative to its parent comment. Sibling comments should have the same identation.
 
+## Useful Code
+
+### getline
+
+Unlike previous assignments where the input files only contain fields separated by spaces, in this assignment, fields are not separated by spaces, and therefore you may need a different way to read the input files. And the function *getline* will now come into play. To read the json file and store the whole json file into a std::string, you can use the following lines of code:
+
+```cpp
+	// assume inputFile is a std::string, containing the file name of the input file.
+        std::ifstream jsonFile(inputFile);
+        if (!jsonFile.is_open()) {
+                std::cerr << "Failed to open the JSON file." << std::endl;
+                exit(1);
+        }
+
+        std::string json_content;
+        std::string line;
+        while (std::getline(jsonFile, line)) {
+                json_content += line;
+        }
+        // don't need this json file anymore, as the content is read into json_content.
+        jsonFile.close();
+```
+
+After these lines, the whole content of the json file will be stored as a string in the std::string variable *json_content*. And you can then parse it to get each individual comment.
+
+### print thumbs up symbol
+
+This line will print the thumbs up symbol, indicating likes.
+
+```
+std::cout << "\U0001F44D " << std::endl;
+```
+
+Of course you can change std::cout to a file stream so as to print the thumbs up symbol into the output file.
+
 ## Program Requirements & Submission Details
 
 In this assignment, you are required to maintain the comments in tree nodes, each comment should be stored in one tree node. You are NOT allowed to use any data structures we have not learned so far, but feel free to use any data structures we have already learned, such as std::string, std::vector, std::list, std::map, std::set, std::pair. **You must use recursion in your program in at least one of your functions.**