Array Reversal Techniques in DSA Python - Build from Scratch

Array Reversal Techniques

📖 Scenario: You are working on a simple program that helps reverse the order of items in a list. This is useful in many real-life situations, like reversing the order of songs in a playlist or flipping the order of steps in a recipe.

🎯 Goal: Build a program that creates a list of numbers, sets up a helper variable, reverses the list using a loop, and then prints the reversed list.

📋 What You'll Learn

Create a list called numbers with these exact values: [10, 20, 30, 40, 50]

Create an empty list called reversed_numbers to store reversed values

Use a for loop with variable i to iterate over the indexes of numbers in reverse order

Append each item from numbers at index i to reversed_numbers

Print the reversed_numbers list

💡 Why This Matters

🌍 Real World

Reversing lists is useful in many daily tasks like undoing actions, reversing playlists, or flipping the order of steps in instructions.

💼 Career

Understanding how to manipulate lists and reverse data is a fundamental skill for programming jobs, especially in data processing and software development.

1

Create the initial list

Create a list called numbers with these exact values: [10, 20, 30, 40, 50]

DSA Python

# Create the list called numbers with values [10, 20, 30, 40, 50]
# Your code here

Hint

Use square brackets to create the list and separate numbers with commas.

2

Set up an empty list for reversed values

Create an empty list called reversed_numbers to store reversed values

DSA Python

numbers = [10, 20, 30, 40, 50]
# Create an empty list called reversed_numbers
# Your code here

Hint

Use empty square brackets to create an empty list.

3

Reverse the list using a for loop

Use a for loop with variable i to iterate over the indexes of numbers in reverse order using range(len(numbers)-1, -1, -1). Inside the loop, append each item from numbers at index i to reversed_numbers

DSA Python

numbers = [10, 20, 30, 40, 50]
reversed_numbers = []
# Use a for loop with i in range(len(numbers)-1, -1, -1) to append numbers[i] to reversed_numbers
# Your code here

Hint

Use range with three arguments to count backwards from the last index to zero.

4

Print the reversed list

Print the reversed_numbers list using print(reversed_numbers)

DSA Python

numbers = [10, 20, 30, 40, 50]
reversed_numbers = []
for i in range(len(numbers)-1, -1, -1):
    reversed_numbers.append(numbers[i])
# Print the reversed_numbers list
# Your code here

Hint

Use the print function to show the reversed list.