2353. Design a Food Rating System

Problem Link

Description

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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.

  <ul>
  	<li><code>foods[i]</code> is the name of the <code>i<sup>th</sup></code> food,</li>
  	<li><code>cuisines[i]</code> is the type of cuisine of the <code>i<sup>th</sup></code> food, and</li>
  	<li><code>ratings[i]</code> is the initial rating of the <code>i<sup>th</sup></code> food.</li>
  </ul>
  </li>
  <li><code>void changeRating(String food, int newRating)</code> Changes the rating of the food item with the name <code>food</code>.</li>
  <li><code>String highestRated(String cuisine)</code> Returns the name of the food item that has the highest rating for the given type of <code>cuisine</code>. If there is a tie, return the item with the <strong>lexicographically smaller</strong> name.</li>
  

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

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Python3

class FoodRatings:
 
    def __init__(self, foods: List[str], cuisines: List[str], ratings: List[int]):
        self.heap = defaultdict(list)
        self.mp = {}
 
        for food, cuisine, rating in zip(foods, cuisines, ratings):
            self.mp[food] = [cuisine, rating]
            heappush(self.heap[cuisine], (-rating, food))
 
    def changeRating(self, food: str, newRating: int) -> None:
        self.mp[food][1] = newRating
        cuisine = self.mp[food][0]
        heappush(self.heap[cuisine], (-newRating, food))
 
    def highestRated(self, cuisine: str) -> str:
        # lazy remove invalid data from the heap
        while self.heap[cuisine] and -self.heap[cuisine][0][0] != self.mp[self.heap[cuisine][0][1]][1]:
            heappop(self.heap[cuisine])
        
        return self.heap[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)