Frequncy Tracker Leetcode

 2671. Frequency Tracker

Design a data structure that keeps track of the values in it and answers some queries regarding their frequencies.

Implement the FrequencyTracker class.

• FrequencyTracker(): Initializes the FrequencyTracker object with an empty array initially.
• void add(int number): Adds number to the data structure.
• void deleteOne(int number): Deletes one occurence of number from the data structure. The data structure may not contain number, and in this case nothing is deleted.
• bool hasFrequency(int frequency): Returns true if there is a number in the data structure that occurs frequency number of times, otherwise, it returns false.

 

Example 1:

Input
["FrequencyTracker", "add", "add", "hasFrequency"]
[[], [3], [3], [2]]
Output
[null, null, null, true]

Explanation
FrequencyTracker frequencyTracker = new FrequencyTracker();
frequencyTracker.add(3); // The data structure now contains [3]
frequencyTracker.add(3); // The data structure now contains [3, 3]
frequencyTracker.hasFrequency(2); // Returns true, because 3 occurs twice

Example 2:

Input
["FrequencyTracker", "add", "deleteOne", "hasFrequency"]
[[], [1], [1], [1]]
Output
[null, null, null, false]

Explanation
FrequencyTracker frequencyTracker = new FrequencyTracker();
frequencyTracker.add(1); // The data structure now contains [1]
frequencyTracker.deleteOne(1); // The data structure becomes empty []
frequencyTracker.hasFrequency(1); // Returns false, because the data structure is empty

Example 3:

Input
["FrequencyTracker", "hasFrequency", "add", "hasFrequency"]
[[], [2], [3], [1]]
Output
[null, false, null, true]

Explanation
FrequencyTracker frequencyTracker = new FrequencyTracker();
frequencyTracker.hasFrequency(2); // Returns false, because the data structure is empty
frequencyTracker.add(3); // The data structure now contains [3]
frequencyTracker.hasFrequency(1); // Returns true, because 3 occurs once

 

Constraints:

• 1 <= number <= 105
• 1 <= frequency <= 105
• At most, 2 * 105 calls will be made to add, deleteOne, and hasFrequency in total.

Solution : 

class FrequencyTracker { public:     unordered_map<int, int>map, frequency ;     FrequencyTracker() {         // FrequencyTracker frequencyTracker = new FrequencyTracker();     }       void add(int number) {                 map[number]++;         int x = map[number];         frequency[x-1] --;         frequency[x] ++ ;     }       void deleteOne(int number) {         if(map[number])         {map[number]--;             int x = map[number];           frequency[x] ++ ;;         frequency[x+1] --;         }     }       bool hasFrequency(int k) {               if(frequency[k])             return true;         return false;               } }; /** * Your FrequencyTracker object will be instantiated and called as such: * FrequencyTracker* obj = new FrequencyTracker(); * obj->add(number); * obj->deleteOne(number); * bool param_3 = obj->hasFrequency(frequency); */