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Occurrences of Each Element in a List

Certification: Basic Level Accuracy: 82.35% Submissions: 34 Points: 5

Write a Python program that counts how many times each element appears in a list and returns a dictionary.

Example 1
    

  • Input: lst = [1, 2, 2, 3, 3, 3]
    • 

  • Output: {1: 1, 2: 2, 3: 3}
    • 

  • Explanation: 
      

    • Step 1: Create an empty dictionary to store the frequency of each element.
      • 

    • Step 2: Iterate through the list, counting occurrences of each element.
      • 

    • Step 3: Element 1 appears once, so add entry {1: 1}.
      • 

    • Step 4: Element 2 appears twice, so add entry {2: 2}.
      • 

    • Step 5: Element 3 appears three times, so add entry {3: 3}.
      • 

    • Step 6: Return the dictionary with all element frequencies.
      • 

    •
Example 2
    

  • Input: lst = [4, 4, 4, 4]
    • 

  • Output: {4: 4}
    • 

  • Explanation: 
      

    • Step 1: Create an empty dictionary to store the frequency of each element.
      • 

    • Step 2: Iterate through the list, counting occurrences of each element.
      • 

    • Step 3: Element 4 appears four times, so add entry {4: 4}.
      • 

    • Step 4: Return the dictionary with the element frequency.
      • 

    •
Constraints
    

  • 1 ≤ len(lst) ≤ 10^3
    • 

  • -10^5 ≤ lst[i] ≤ 10^5
    • 

  • Time Complexity: O(n) where n is the length of the input list
    • 

  • Space Complexity: O(n) to store the frequency dictionary
    •
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Hint
Solution

Solution Hints

    
  
  • Use the Counter module from collections to count elements.
    • 
  
  • Convert the result to a dictionary.
    •

Steps to solve by this approach:

 Step 1: Import the Counter class from the collections module.

 Step 2: Apply Counter to the input list to count occurrences of each element.

 Step 3: Convert the Counter object to a regular dictionary.

 Step 4: Return the dictionary mapping elements to their frequency counts.

 Step 5: Handle the case of an empty input list by returning an empty dictionary.

Submitted Code :