Shuffle - codepath/compsci_guides GitHub Wiki

TIP102 Unit 1 Session 1 Standard (Click for link to problem statements)

Problem Highlights

• 💡 Difficulty: Easy
• ⏰ Time to complete: 5 mins
• 🛠️ Topics: Lists, Iteration

U-nderstand

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

• Q: What is the function's input?

  • A: The input is a list cards of 2n elements in the form [x1, x2, ..., xn, y1, y2, ..., yn].

• Q: What should the function return?

  • A: The function should return a list where the elements are shuffled to form [x1, y1, x2, y2, ..., xn, yn].

• Q: Can the input list have an odd number of elements?

  • A: No, the problem statement specifies that the list will have 2n elements, so the number of elements will always be even.

• Q: Is it acceptable to create a new list to store the shuffled elements?

  • A: Yes, the problem does not restrict the creation of a new list.

• The function shuffle() should take a list of 2n elements in the format [x1, x2, ..., xn, y1, y2, ..., yn] and return a new list in the format [x1, y1, x2, y2, ..., xn, yn].

HAPPY CASE
Input: ['Joker', 'Queen', 2, 3, 'Ace', 7]
Expected Output: ['Joker', 3, 'Queen', 'Ace', 2, 7]

Input: [9, 2, 3, 'Joker', 'Joker', 3, 2, 9]
Expected Output: [9, 'Joker', 2, 3, 3, 2, 'Joker', 9]

EDGE CASE
Input: [10, 10, 2, 2]
Expected Output: [10, 2, 10, 2]
    
Input: [] (empty list)
Expected Output: []

P-lan

Plan the solution with appropriate visualizations and pseudocode.

General Idea: Calculate the midpoint of the list, then iterate through the first half and append elements from both halves to a new list in the specified order.

1. Define the function `shuffle(cards)`.
2. Calculate `n` as half the length of the list `cards`.
3. Initialize an empty list `shuffled` to hold the result.
4. Iterate over the range from 0 to `n - 1`.
5. For each index `i`, append `cards[i]` and `cards[i + n]` to the `shuffled` list.
6. Return the `shuffled` list.

⚠️ Common Mistakes

• Forgetting to calculate the midpoint correctly.
• Attempting to access indices that are out of range.

I-mplement

Implement the code to solve the algorithm.

def shuffle(cards):
    n = len(cards) // 2
    shuffled = []
    
    for i in range(n):
        shuffled.append(cards[i])
        shuffled.append(cards[i + n])
    
    return shuffled