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Extract the First and Last Elements of a List

Certification: Basic Level Accuracy: 61.31% Submissions: 168 Points: 5

Write a Python program that extracts the first and last elements of a given list.

Example 1
    
  
  • Input: [1, 2, 3, 4, 5]
    • 
  
  • Output: [1, 5]
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  • Explanation: 
    
      
      
    • Step 1: Get the first element of the list [1, 2, 3, 4, 5], which is 1.
      • 
      
    • Step 2: Get the last element of the list [1, 2, 3, 4, 5], which is 5.
      • 
      
    • Step 3: Create a new list containing these two elements: [1, 5].
      • 
      
    • Step 4: Return the new list [1, 5].
      • 
    
    
  
    •
Example 2
    
  
  • Input: ["apple"]
    • 
  
  • Output: ["apple", "apple"]
    • 
  
  • Explanation: 
    
      
      
    • Step 1: Get the first element of the list ["apple"], which is "apple".
      • 
      
    • Step 2: Get the last element of the list ["apple"], which is also "apple" since there is only one element.
      • 
      
    • Step 3: Create a new list containing these two elements: ["apple", "apple"].
      • 
      
    • Step 4: Return the new list ["apple", "apple"].
      • 
    
    
  
    •
Constraints
    
  
  • 1 ≤ len(list) ≤ 10^6
    • 
  
  • Elements can be of any data type
    • 
  
  • Time Complexity: O(1)
    • 
  
  • Space Complexity: O(1)
    •
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Hint
Solution

Solution Hints

 
     
  
  • Use indexing: [lst[0], lst[-1]]
    •  
  
  • Use list unpacking: first, *middle, last = lst; [first, last]
    •  
  
  • Handle single element lists: [lst[0], lst[0]] if len(lst) == 1 else [lst[0], lst[-1]]
    •  
  
  • Use list comprehension with conditions: [lst[i] for i in (0, -1 if len(lst) > 1 else 0)]
    •

Here's the step-by-step solution to extract the first and last elements of a list:

  • Create a function called first_last_elements that accepts a list parameter lst.

  • Use list indexing to access the first element of the list: lst[0]

  • Use list indexing to access the last element of the list: lst[-1] (Python's way of accessing the last element)

  • Return both elements as a new list: return [lst[0], lst[-1]]

  • Call the function with the example list [1, 2, 3, 4, 5]

  • Print the result, which will be [1, 5]

Submitted Code :