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Intersection of Two Lists

Certification: Basic Level Accuracy: 84.62% Submissions: 39 Points: 5

Write a Python program that finds the common elements between two lists. The output should be a list containing elements that appear in both lists.

Example 1
    

  • Input: list1 = [1, 2, 3, 4], list2 = [3, 4, 5, 6]
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  • Output: [3, 4]
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  • Explanation: 
      

    • Step 1: Create a set from the first list for O(1) lookups.
      • 

    • Step 2: Iterate through the second list, checking if each element exists in the set.
      • 

    • Step 3: If an element is found in both lists, add it to the result list.
      • 

    • Step 4: The elements 3 and 4 appear in both lists, so return [3, 4].
      • 

    •
Example 2
    

  • Input: list1 = [10, 20, 30], list2 = [40, 50, 60]
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  • Output: []
    • 

  • Explanation: 
      

    • Step 1: Create a set from the first list for O(1) lookups.
      • 

    • Step 2: Iterate through the second list, checking if each element exists in the set.
      • 

    • Step 3: No common elements are found between the two lists.
      • 

    • Step 4: Return an empty list [].
      • 

    •
Constraints
    

  • 1 ≤ len(list1), len(list2) ≤ 10^3
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  • -10^5 ≤ list1[i], list2[i] ≤ 10^5
    • 

  • Time Complexity: O(n) where n is the total number of elements in both lists
    • 

  • Space Complexity: O(n) to store the elements from the first list in a set
    •
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Hint
Solution

Solution Hints

    
  
  • Use set intersection (&) to find common elements efficiently.
    • 
  
  • Convert lists to sets to remove duplicates before finding the intersection.
    •

Steps to solve by this approach:

 Step 1: Convert both input lists to sets to eliminate duplicates.

 Step 2: Use the set intersection operator (&) to find common elements.

 Step 3: Convert the resulting set back to a list.

 Step 4: Return the list of common elements.

 Step 5: Handle the case where there are no common elements by returning an empty list.

Submitted Code :