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Top K Frequent Elements

Certification: Intermediate Level Accuracy: 100% Submissions: 1 Points: 10

Write a JavaScript program to find the k most frequent elements in an array. Given an integer array nums and an integer k, return the k most frequent elements. The answer can be returned in any order.

Example 1
    
  
  • Input: nums = [1,1,1,2,2,3], k = 2
    • 
  
  • Output: [1,2]
    • 
  
  • Explanation: 
    • Count the frequency of each element in the array. 
    • Element 1 appears 3 times, element 2 appears 2 times, element 3 appears 1 time. 
    • We need the top 2 most frequent elements. 
    • Elements 1 and 2 are the most frequent, so we return [1,2].
    •
Example 2
    
  
  • Input: nums = [1], k = 1
    • 
  
  • Output: [1]
    • 
  
  • Explanation: 
    • The array contains only one element. 
    • Element 1 appears 1 time. 
    • We need the top 1 most frequent element. 
    • The only element 1 is returned as [1].
    •
Constraints
    
  
  • 1 ≤ nums.length ≤ 10^5
    • 
  
  • -10^4 ≤ nums[i] ≤ 10^4
    • 
  
  • k is in the range [1, number of unique elements in array]
    • 
  
  • Time Complexity: O(n log k)
    • 
  
  • Space Complexity: O(n)
    •
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Hint
Solution

Solution Hints

    
  
  • Use a hash map to count the frequency of each element
    • 
  
  • Use a min-heap to keep track of the k most frequent elements
    • 
  
  • Iterate through the frequency map and maintain a heap of size k
    • 
  
  • If heap size exceeds k, remove the least frequent element
    • 
  
  • Extract all elements from the heap to get the final result
    •

Steps to solve by this approach:

  Step 1: Create a hash map to store the frequency of each element in the input array.

 Step 2: Iterate through the array and count occurrences of each element using the frequency map.

 Step 3: Convert the frequency map to an array of [element, frequency] pairs for easier manipulation.

 Step 4: Sort the array of pairs in descending order based on frequency values.

 Step 5: Extract the first k elements from the sorted array to get the most frequent elements.

 Step 6: Create a result array containing only the element values (not frequencies).

 Step 7: Return the result array containing the k most frequent elements.

Submitted Code :