17_Design_a_Food_Rating_System.cpp

// 2353. Design a Food Rating System

// Design a food rating system that can do the following:

// Modify the rating of a food item listed in the system.
// Return the highest-rated food item for a type of cuisine in the system.
// Implement the FoodRatings class:

// FoodRatings(String[] foods, String[] cuisines, int[] ratings) Initializes the system. The food items are described by foods, cuisines and ratings, all of which have a length of n.
// foods[i] is the name of the ith food,
// cuisines[i] is the type of cuisine of the ith food, and
// ratings[i] is the initial rating of the ith food.
// void changeRating(String food, int newRating) Changes the rating of the food item with the name food.
// String highestRated(String cuisine) Returns the name of the food item that has the highest rating for the given type of cuisine. If there is a tie, return the item with the lexicographically smaller name.
// Note that a string x is lexicographically smaller than string y if x comes before y in dictionary order, that is, either x is a prefix of y, or if i is the first position such that x[i] != y[i], then x[i] comes before y[i] in alphabetic order.

 

// Example 1:

// Input
// ["FoodRatings", "highestRated", "highestRated", "changeRating", "highestRated", "changeRating", "highestRated"]
// [[["kimchi", "miso", "sushi", "moussaka", "ramen", "bulgogi"], ["korean", "japanese", "japanese", "greek", "japanese", "korean"], [9, 12, 8, 15, 14, 7]], ["korean"], ["japanese"], ["sushi", 16], ["japanese"], ["ramen", 16], ["japanese"]]
// Output
// [null, "kimchi", "ramen", null, "sushi", null, "ramen"]

// Explanation
// FoodRatings foodRatings = new FoodRatings(["kimchi", "miso", "sushi", "moussaka", "ramen", "bulgogi"], ["korean", "japanese", "japanese", "greek", "japanese", "korean"], [9, 12, 8, 15, 14, 7]);
// foodRatings.highestRated("korean"); // return "kimchi"
//                                     // "kimchi" is the highest rated korean food with a rating of 9.
// foodRatings.highestRated("japanese"); // return "ramen"
//                                       // "ramen" is the highest rated japanese food with a rating of 14.
// foodRatings.changeRating("sushi", 16); // "sushi" now has a rating of 16.
// foodRatings.highestRated("japanese"); // return "sushi"
//                                       // "sushi" is the highest rated japanese food with a rating of 16.
// foodRatings.changeRating("ramen", 16); // "ramen" now has a rating of 16.
// foodRatings.highestRated("japanese"); // return "ramen"
//                                       // Both "sushi" and "ramen" have a rating of 16.
//                                       // However, "ramen" is lexicographically smaller than "sushi".
 

// Constraints:

// 1 <= n <= 2 * 104
// n == foods.length == cuisines.length == ratings.length
// 1 <= foods[i].length, cuisines[i].length <= 10
// foods[i], cuisines[i] consist of lowercase English letters.
// 1 <= ratings[i] <= 108
// All the strings in foods are distinct.
// food will be the name of a food item in the system across all calls to changeRating.
// cuisine will be a type of cuisine of at least one food item in the system across all calls to highestRated.
// At most 2 * 104 calls in total will be made to changeRating and highestRated.


class FoodRatings {
    unordered_map<string, string> foodToCuisine;
    unordered_map<string, int> foodToRating;
    unordered_map<string, set<pair<int, string>>> cuisineToFoods;

public:
    FoodRatings(vector<string>& foods, vector<string>& cuisines, vector<int>& ratings) {
        for (int i = 0; i < foods.size(); ++i) {
            foodToCuisine[foods[i]] = cuisines[i];
            foodToRating[foods[i]] = ratings[i];
            cuisineToFoods[cuisines[i]].insert({-ratings[i], foods[i]});
        }
    }
    
    void changeRating(string food, int newRating) {
        string cuisine = foodToCuisine[food];
        int oldRating = foodToRating[food];
        cuisineToFoods[cuisine].erase({-oldRating, food});
        cuisineToFoods[cuisine].insert({-newRating, food});
        foodToRating[food] = newRating;
    }
    
    string highestRated(string cuisine) {
        return cuisineToFoods[cuisine].begin()->second;
    }
};