Package g2601_2700.s2671_frequency_tracker

Class FrequencyTracker

java.lang.Object
g2601_2700.s2671_frequency_tracker.FrequencyTracker
public class FrequencyTracker extends java.lang.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 Summary

    Constructors
    Constructor
    Description
    FrequencyTracker()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    add(int number)
     
    void
    deleteOne(int number)
     
    boolean
    hasFrequency(int frequency)
     

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • 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)