Reverse List - codepath/compsci_guides GitHub Wiki

Unit 1 Session 2 (Click for link to problem statements)

U-nderstand

Understand what the interviewer is asking for by using test cases and questions about the problem.

P-lan

Plan the solution with appropriate visualizations and pseudocode.

General Idea: Create a reversed list by looping through each element in reverse. and adding them to the beginning of another list.

1) Create a new list to hold the reversed values
2) Loop through each value in the original list, starting at the beginning index and incrementing backwards by 1
  a) Add each value to the end of the new list
3) Return the new list

**Alternative Ideas:** 
- Loop through each value in the original list in the forwards direction, and use the `insert()` function to add elements to the beginning of the results list. 
- Use string slicing syntax. 

⚠️ Common Mistakes

• To visualize this strategy, it might help to try drawing out an example.
  • You've most likely reversed a "list" using this strategy in real life. For example, have you ever had to reverse the order of a stack of papers? How did you do it?

I-mplement

def reverse_list(numbers):
    reversed_list = []
    for i in range(len(numbers) - 1, -1, -1):
        reversed_list.append(numbers[i])
    return reversed_list

Alternative Solution:

def reverse_list(numbers):
    reversed_list = []
    for number in numbers:
        reversed_list.insert(0, number)
    return reversed_list

Alternative Solution:

def reverse_list(numbers):
    return numbers[::-1]