Introduction

In this blog post, we will explore how to solve the LeetCode problem "2409" 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

Alice and Bob are traveling to Rome for separate business meetings. You are given 4 strings arriveAlice, leaveAlice, arriveBob, and leaveBob. Alice will be in the city from the dates arriveAlice to leaveAlice (inclusive), while Bob will be in the city from the dates arriveBob to leaveBob (inclusive). Each will be a 5-character string in the format "MM-DD", corresponding to the month and day of the date. Return the total number of days that Alice and Bob are in Rome together. You can assume that all dates occur in the same calendar year, which is not a leap year. Note that the number of days per month can be represented as: [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]. Example 1: Input: arriveAlice = "08-15", leaveAlice = "08-18", arriveBob = "08-16", leaveBob = "08-19" Output: 3 Explanation: Alice will be in Rome from August 15 to August 18. Bob will be in Rome from August 16 to August 19. They are both in Rome together on August 16th, 17th, and 18th, so the answer is 3. Example 2: Input: arriveAlice = "10-01", leaveAlice = "10-31", arriveBob = "11-01", leaveBob = "12-31" Output: 0 Explanation: There is no day when Alice and Bob are in Rome together, so we return 0. Constraints: All dates are provided in the format "MM-DD". Alice and Bob's arrival dates are earlier than or equal to their leaving dates. The given dates are valid dates of a non-leap year.

Explanation

Here's a breakdown of the approach, complexities, and Python code:

• Approach:

  • Convert the date strings into a numerical representation (day of the year) for easier comparison.
  • Determine the overlapping period between Alice and Bob's stays in Rome.
  • Calculate the number of days in the overlapping period.

• Complexity:

  • Runtime Complexity: O(1) - The calculations are constant time since we are only dealing with four date strings.
  • Storage Complexity: O(1) - We use a fixed number of variables regardless of the input.

Code

    def count_days_together(arriveAlice: str, leaveAlice: str, arriveBob: str, leaveBob: str) -> int:
    """
    Calculates the number of days Alice and Bob are in Rome together.
    """

    def date_to_days(date: str) -> int:
        """Converts a date string (MM-DD) to the day of the year."""
        month, day = map(int, date.split('-'))
        days_in_month = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
        day_of_year = day
        for i in range(month - 1):
            day_of_year += days_in_month[i]
        return day_of_year

    alice_arrive = date_to_days(arriveAlice)
    alice_leave = date_to_days(leaveAlice)
    bob_arrive = date_to_days(arriveBob)
    bob_leave = date_to_days(leaveBob)

    overlap_start = max(alice_arrive, bob_arrive)
    overlap_end = min(alice_leave, bob_leave)

    if overlap_start <= overlap_end:
        return overlap_end - overlap_start + 1
    else:
        return 0