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Formatted question description: https://leetcode.ca/all/2353.html

# 2353. Design a Food Rating System

• Difficulty: Medium.
• Related Topics: Hash Table, Design, Heap (Priority Queue), Ordered Set.
• Similar Questions: Design a Number Container System.

## 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.

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 (Java, C++, Python)

• 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])) {
} else {
TreeSet<Food> pq = new TreeSet<>(new Comp());
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;
}

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);
*/

• from sortedcontainers import SortedSet

class FoodRatings:
def __init__(self, foods: List[str], cuisines: List[str], ratings: List[int]):
self.mp = {}
self.t = defaultdict(lambda: SortedSet(key=lambda x: (-x[0], x[1])))

for a, b, c in zip(foods, cuisines, ratings):
self.mp[a] = (b, c)

def changeRating(self, food: str, newRating: int) -> None:
b, c = self.mp[food]
self.mp[food] = (b, newRating)
self.t[b].remove((c, food))

def highestRated(self, cuisine: str) -> str:
return self.t[cuisine][0][1]

# Your FoodRatings object will be instantiated and called as such:
# obj = FoodRatings(foods, cuisines, ratings)
# obj.changeRating(food,newRating)
# param_2 = obj.highestRated(cuisine)

############

# 2353. Design a Food Rating System
# https://leetcode.com/problems/design-a-food-rating-system/

from sortedcontainers import SortedList

class FoodRatings:

def __init__(self, foods: List[str], cuisines: List[str], ratings: List[int]):
self.mp = {}
self.A = defaultdict(SortedList)

for food, cuisine, rating in zip(foods, cuisines, ratings):
self.mp[food] = (cuisine, rating)

def changeRating(self, food: str, newRating: int) -> None:
cuisine, rating = self.mp[food]
self.mp[food] = (cuisine, newRating)
self.A[cuisine].remove((-rating, food))

def highestRated(self, cuisine: str) -> str:
return self.A[cuisine][0][1]

# Your FoodRatings object will be instantiated and called as such:
# obj = FoodRatings(foods, cuisines, ratings)
# obj.changeRating(food,newRating)
# param_2 = obj.highestRated(cuisine)


• using pis = pair<int, string>;

class FoodRatings {
map<string, pis> mp;
map<string, set<pis>> t;

public:
FoodRatings(vector<string>& foods, vector<string>& cuisines, vector<int>& ratings) {
int n = foods.size();
for (int i = 0; i < n; ++i) {
string a = foods[i], b = cuisines[i];
int c = ratings[i];
mp[a] = pis(c, b);
t[b].insert(pis(-c, a));
}
}

void changeRating(string food, int newRating) {
pis& p = mp[food];
t[p.second].erase(pis(-p.first, food));
p.first = newRating;
t[p.second].insert(pis(-p.first, food));
}

string highestRated(string cuisine) {
return t[cuisine].begin()->second;
}
};

/**
* 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);
*/


Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).