Introduction

In this blog post, we will explore how to solve the LeetCode problem "950" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like Chatmagic, we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

Problem Statement

You are given an integer array deck. There is a deck of cards where every card has a unique integer. The integer on the ith card is deck[i]. You can order the deck in any order you want. Initially, all the cards start face down (unrevealed) in one deck. You will do the following steps repeatedly until all cards are revealed: Take the top card of the deck, reveal it, and take it out of the deck. If there are still cards in the deck then put the next top card of the deck at the bottom of the deck. If there are still unrevealed cards, go back to step 1. Otherwise, stop. Return an ordering of the deck that would reveal the cards in increasing order. Note that the first entry in the answer is considered to be the top of the deck. Example 1: Input: deck = [17,13,11,2,3,5,7] Output: [2,13,3,11,5,17,7] Explanation: We get the deck in the order [17,13,11,2,3,5,7] (this order does not matter), and reorder it. After reordering, the deck starts as [2,13,3,11,5,17,7], where 2 is the top of the deck. We reveal 2, and move 13 to the bottom. The deck is now [3,11,5,17,7,13]. We reveal 3, and move 11 to the bottom. The deck is now [5,17,7,13,11]. We reveal 5, and move 17 to the bottom. The deck is now [7,13,11,17]. We reveal 7, and move 13 to the bottom. The deck is now [11,17,13]. We reveal 11, and move 17 to the bottom. The deck is now [13,17]. We reveal 13, and move 17 to the bottom. The deck is now [17]. We reveal 17. Since all the cards revealed are in increasing order, the answer is correct. Example 2: Input: deck = [1,1000] Output: [1,1000] Constraints: 1 <= deck.length <= 1000 1 <= deck[i] <= 106 All the values of deck are unique.

Explanation

Here's a breakdown of the solution and the Python code:

• High-Level Approach:

  • Simulate the reverse process. Instead of revealing cards, we reconstruct the deck from the revealed order.
  • Use a queue (deque) to represent the deck. Start with a queue representing the indices of the final ordered deck.
  • Iterate through the sorted cards in reverse order. For each card, place it at the correct index in the result array by simulating the "move to the bottom" operation in reverse.

• Complexity:

  • Runtime: O(n log n) due to sorting the deck. The queue operations are O(n).
  • Storage: O(n) for the sorted indices and the result array.

Code

    from collections import deque

def deckRevealedIncreasing(deck):
    """
    Reorders the deck to reveal cards in increasing order.

    Args:
        deck: A list of integers representing the deck of cards.

    Returns:
        A list of integers representing the reordered deck.
    """

    n = len(deck)
    indices = deque(range(n))  # Queue of indices
    result = [0] * n
    deck.sort()

    for card in deck:
        index = indices.popleft()
        result[index] = card
        if indices:
            indices.append(indices.popleft())

    return result