Python program to sort and reverse a given list

When working with lists in Python, you often need to sort or reverse them without modifying the original list. Python provides sorted() and reversed() functions that return new objects, unlike sort() and reverse() which modify the list in-place.

Problem Statement

Given a list of numbers, create a reversed version and a sorted version without changing the original list.

Example Input and Output

If the input is l = [2, 5, 8, 6, 3, 4, 7, 9], the output should be ?

Reversed: [9, 7, 4, 3, 6, 8, 5, 2]
Sorted: [2, 3, 4, 5, 6, 7, 8, 9]

Solution Approach

To solve this problem, we will follow these steps ?

• rev := create a list from reversed() function output
• Display the reversed list
• srt := sort the list using sorted() function
• Display the sorted list

Implementation

def solve(l):
    rev = list(reversed(l))
    print("Reversed:", rev)
    
    srt = sorted(l)
    print("Sorted:", srt)

# Test the function
l = [2, 5, 8, 6, 3, 4, 7, 9]
solve(l)

# Verify original list is unchanged
print("Original:", l)

Reversed: [9, 7, 4, 3, 6, 8, 5, 2]
Sorted: [2, 3, 4, 5, 6, 7, 8, 9]
Original: [2, 5, 8, 6, 3, 4, 7, 9]

How It Works

The reversed() function returns an iterator that accesses the list in reverse order. Converting it to a list with list() creates a new reversed list. The sorted() function returns a new sorted list without modifying the original.

Key Points

• reversed() returns an iterator, so wrap it with list()
• sorted() directly returns a new sorted list
• Original list remains unchanged throughout the process
• Both functions work with any iterable, not just lists

Conclusion

Use reversed() and sorted() to create new reversed and sorted versions of a list without modifying the original. This approach preserves data integrity while providing the required transformations.