Package g2601_2700.s2671_frequency_tracker

Class FrequencyTracker

java.lang.Object
g2601_2700.s2671_frequency_tracker.FrequencyTracker
public class FrequencyTracker extends Object
2671 - Frequency Tracker.

Medium

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 occurrence 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.

  • Constructor Details

    • FrequencyTracker

      public FrequencyTracker()

  • Method Details

    • add

      public void add(int number)

    • deleteOne

      public void deleteOne(int number)

    • hasFrequency

      public boolean hasFrequency(int frequency)