Today I have done leetcode's December LeetCoding Challenge with cpp.

December LeetCoding Challenge 17

Description

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.

  <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

class Compare {
  using pis = pair<int, string>;
public:
  bool operator()(pis below, pis above)
  {
    if (below.first < above.first) {
      return true;
    }
    else if (below.first == above.first && below.second > above.second) {
      return true;
    }

    return false;
  }
};
 
class FoodRatings {
  using pis = pair<int, string>;
  using pq = priority_queue<pis, vector<pis>, Compare>;
  map<string, pq> mp;
  map<string, int> foodRating;
  map<string, string> cuisineRating;
public:
  FoodRatings(vector<string>& foods, vector<string>& cuisines, vector<int>& ratings) {
    for(int i = 0; i < foods.size(); ++i) {
      foodRating[foods[i]] = ratings[i];
      cuisineRating[foods[i]] = cuisines[i];
      mp[cuisines[i]].push({ratings[i], foods[i]});
    } 
  }
  
  void changeRating(string food, int newRating) {
    mp[cuisineRating[food]].push({newRating, food});
    foodRating[food] = newRating;
  }
  
  string highestRated(string cuisine) {
    auto food = mp[cuisine].top();
    while(foodRating[food.second] != food.first) {
      mp[cuisine].pop();
      food = mp[cuisine].top();
    }
    return food.second;
  }
};

// Accepted
// 77/77 cases passed (516 ms)
// Your runtime beats 22.49 % of cpp submissions
// Your memory usage beats 81.82 % of cpp submissions (162.5 MB)