adding provided code

hws/04_yelp_businesses/README.md

@@ -46,12 +46,114 @@ Keep in mind that users can select multiple categories, in the above two screens
 - Indian
 - Chinese
 
-When your program is executed, it produces the businesses which fall into any of the chosen categories, and are located in this zipcode area. For each business, your program will print to the output something similar to what Yelp does. The following is an example:
+If multiple categories are supplied from the command line, these categories will be separated by a single space.
+
+When your program is executed, it produces the businesses which fall into any of the chosen categories, and are located in this zipcode area. For each business, your program will print to the output file something similar to what Yelp does. The following is an example:
 
 ![alt text](images/alibaba.jpg "Alibaba")
 
+The businesses showed in your output file should be sorted based on the rating of the business, with higher rated businesses being showed before lower rated businesses. For any two businesses which have the same rating, for example, both are 4.5, then in your output file, keep the order of these two as they appear in the input file.
+
 ## Provided Code
 
+Several helper functions are provided for you to parse the json file. All of them expect the caller to provide the one line from the json file as the sole argument, in the format of an std::string.
+
+1. Get Business Name:
+
+```cpp
+std::string getName(std::string& line){
+        int start = 0;
+        // starting from the position start, and search the string variable line,
+        // to find the first name string.
+        int key_start = line.find("name", start);
+        int value_start = key_start + 7;
+        // remind them to use escape.
+        int value_end = line.find("\"", value_start);
+        int len = value_end - value_start;
+        // go from start to end, but exclude the character at end.
+        // when we use the substr(start, length) function on a std::string,
+        // the substring includes the character at the start position,
+        // and the length of the substring is length.
+        // It does not include the character at the position start + length.
+        std::string name = line.substr(value_start, len);
+        return name;
+}
+```
+
+2. Get Categories:
+
+```cpp
+std::string getCategories(std::string& line){
+        int start = 0;
+        // starting from the position start, and search the string variable line,
+        // to find the first categories string.
+        int key_start = line.find("categories", start);
+        int value_start = key_start + 13;
+        // remind them to use escape.
+        int value_end = line.find("\"", value_start);
+        int len = value_end - value_start;
+        // go from start to end, but exclude the character at end.
+        // when we use the substr(start, length) function on a std::string,
+        // the substring includes the character at the start position,
+        // and the length of the substring is length.
+        // It does not include the character at the position start + length.
+        std::string categories = line.substr(value_start, len);
+        return categories;
+}
+```
+
+3. Get Rating:
+
+```cpp
+double getRating(std::string& line){
+        int start = 0;
+        // starting from the position start, and search the string variable line,
+        // to find the first stars string.
+        int key_start = line.find("stars", start);
+        int value_start = key_start + 7;
+        // remind them to use escape.
+        int value_end = line.find("\"", value_start);
+        // -1 here because this is not a string.
+        int len = value_end - value_start - 1;
+        // go from start to end, but exclude the character at end.
+        // when we use the substr(start, length) function on a std::string,
+        // the substring includes the character at the start position,
+        // and the length of the substring is length.
+        // It does not include the character at the position start + length.
+        // convert this string to a double
+        double stars = stod(line.substr(value_start, len));
+        return stars;
+}
+```
+
+4. Get Price Level:
+
+```cpp
+int getPrice(std::string& line){
+        int start = 0;
+        // starting from the position start, and search the string variable line,
+        // to find the first RestaurantsPriceRange2 string.
+        int key_start = line.find("RestaurantsPriceRange2", start);
+        // if not found, return now
+        if(key_start == std::string::npos){
+                return -1;
+        }
+        int value_start = key_start + 25;
+        // remind them to use escape.
+        int value_end = line.find("\"", value_start);
+        // -1 here because this is not a string.
+        int len = value_end - value_start;
+        // go from start to end, but exclude the character at end.
+        // when we use the substr(start, length) function on a std::string,
+        // the substring includes the character at the start position,
+        // and the length of the substring is length.
+        // It does not include the character at the position start + length.
+        // convert this string to an integer
+        int price = stoi(line.substr(value_start, len));
+        return price;
+}
+```
+
 ## Program Requirements & Submission Details
 
 In this assignment, **you must use std::list to store the businesses which match with what the user is searching for**.