LeetCode-in-Java

2353. Design a Food Rating System

Medium

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.

Solution

import java.util.Comparator;
import java.util.HashMap;
import java.util.TreeSet;

public class FoodRatings {
    private HashMap<String, TreeSet<Food>> cus = new HashMap<>();
    private HashMap<String, Food> foodHashMap = new HashMap<>();

    public FoodRatings(String[] foods, String[] cuisines, int[] ratings) {
        for (int i = 0; i < foods.length; i++) {
            Food food = new Food(foods[i], ratings[i], cuisines[i]);
            foodHashMap.put(foods[i], food);
            if (cus.containsKey(cuisines[i])) {
                cus.get(cuisines[i]).add(food);
            } else {
                TreeSet<Food> pq = new TreeSet<>(new Comp());
                pq.add(food);
                cus.put(cuisines[i], pq);
            }
        }
    }

    public void changeRating(String food, int newRating) {
        Food dish = foodHashMap.get(food);
        TreeSet<Food> pq = cus.get(dish.cus);
        pq.remove(dish);
        dish.rating = newRating;
        pq.add(dish);
    }

    public String highestRated(String cuisine) {
        return cus.get(cuisine).first().foodItem;
    }

    private static class Comp implements Comparator<Food> {
        public int compare(Food f1, Food f2) {
            if (f1.rating == f2.rating) {
                return f1.foodItem.compareTo(f2.foodItem);
            }
            return Integer.compare(f2.rating, f1.rating);
        }
    }

    private static class Food {
        private String foodItem;
        private String cus;
        private int rating;

        Food(String food, int rating, String cus) {
            this.foodItem = food;
            this.rating = rating;
            this.cus = cus;
        }
    }
}

/*
 * 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);
 */

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