[Solved] Design a Food Rating System LeetCode Contest Problem

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.

Design a Food Rating System LeetCode Contest

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.

Solution

class FoodRatings {
public:
    unordered_map<string, map<int, set<string>>> cuisine2rateAndFood;
    unordered_map<string, pair<int, string>> food2cuisineAndRate;
    FoodRatings(vector<string>& foods, vector<string>& cuisines, vector<int>& ratings) {
        int n = foods.size();
        for (int i = 0; i < n; ++i) {
            cuisine2rateAndFood[cuisines[i]][ratings[i]].insert(foods[i]);
            food2cuisineAndRate[foods[i]] = make_pair(ratings[i], cuisines[i]);
        }
    }
    
    void changeRating(string food, int newRating) {
        auto [prevRating, cuisine] = food2cuisineAndRate[food];
        cuisine2rateAndFood[cuisine][prevRating].erase(food);
        if (cuisine2rateAndFood[cuisine][prevRating].empty()) {
            cuisine2rateAndFood[cuisine].erase(prevRating);
        }
        cuisine2rateAndFood[cuisine][newRating].insert(food);
        
        food2cuisineAndRate[food].first = newRating;
    }
    
    string highestRated(string cuisine) {
        auto foodSet = cuisine2rateAndFood[cuisine].rbegin()->second;
        return *foodSet.begin();
    }
};

/**
 * Your FoodRatings object will be instantiated and called as such:
 * FoodRatings* obj = new FoodRatings(foods, cuisines, ratings);
 * obj->changeRating(food,newRating);
 * string param_2 = obj->highestRated(cuisine);
 */

from sortedcontainers import SortedSet

        
class FoodRatings:
    def __init__(self, foods: List[str], cuisine: List[str], ratings: List[int]):
        self.cuisines = defaultdict(lambda: SortedSet(key=lambda x: (-x[0], x[1])))
        self.food_to_cuisine = dict()
        self.food_to_rating = dict()
        
        for index in range(len(foods)):
            _cuisine, food, rating = cu[index], foods[index], ratings[index]
            
            self.cuisines[_cuisine].add((rating, food))
            self.food_to_cuisine[food] = _cuisine
            self.food_to_rating[food] = rating
            
    def changeRating(self, food: str, new_rating: int) -> None:
        old_rating = self.food_to_rating[food]
        cuisine = self.food_to_cuisine[food]
        
        self.cuisines[cuisine].discard((old_rating, food))
        self.cuisines[cuisine].add((new_rating, food))
        self.food_to_rating[food] = new_rating
        
    def highestRated(self, cuisine: str) -> str:
        return self.cuisines[cuisine][0][1]

class FoodRatings {
	Map<String, TreeSet> cuisineMap;
	Map<String, Food> foodMap;
	TreeSet foodSet;

	public FoodRatings(String[] foods, String[] cuisines, int[] ratings) {
		foodMap = new HashMap<>();
		cuisineMap = new HashMap<>();

		for (int i = 0; i < foods.length; ++i) {
			Food food = new Food(foods[i], cuisines[i], ratings[i]);
			foodMap.put(food.name, food);
			if (!cuisineMap.containsKey(food.cuisine)) {
				cuisineMap.put(food.cuisine, new TreeSet<>((a, b) -> a.rating == b.rating ?
						a.name.compareTo(b.name) : b.rating - a.rating));
			}
			cuisineMap.get(food.cuisine).add(food);
		}
	}

	public void changeRating(String food, int newRating) {
		Food f = foodMap.get(food);
		foodSet = cuisineMap.get(f.cuisine);
		foodSet.remove(f);
		f.rating = newRating;
		foodSet.add(f);
	}

	public String highestRated(String cuisine) {
		foodSet = cuisineMap.get(cuisine);
		return foodSet.first().name;
	}
}

class Food {
	String name;
	String cuisine;
	int rating;

	Food(String name, String cuisine, int rating) {
		this.name = name;
		this.rating = rating;
		this.cuisine = cuisine;
	}
}

Happy Learning – If you require any further information, feel free to contact me.