Katkat
Back

Count business days excluding holidays

AirtableSoftware Engineer · Onsite
MediumSoftware EngineerOnsiteCoding & Algorithms

Last updated

This problem tests date manipulation skills and the ability to efficiently calculate working day durations while accounting for dynamic holiday schedules.

Problem Statement

Given a start date, an end date (inclusive), and a list of specific holiday dates, write a function that returns the total number of business days between the two dates. Business days are defined as Monday through Friday. Holidays are specific dates (YYYY-MM-DD strings) that should be excluded even if they fall on a weekday.

Function Signature

def count_business_days(start_date: str, end_date: str, holidays: list[str]) -> int:
    pass

Constraints

  • Dates are provided in 'YYYY-MM-DD' format.
  • The date range can span several years.
  • holidays list may contain dates that fall on weekends.

Examples

Example 1: Input: start_date = "2023-12-25", end_date = "2023-12-29", holidays = ["2023-12-25"] Output: 4 Explanation: 2023-12-25 is a Monday (holiday), 26-29 are Tuesday-Friday (4 days).

Example 2: Input: start_date = "2023-01-01", end_date = "2023-01-07", holidays = [] Output: 5 Explanation: Monday (Jan 2) through Friday (Jan 6) are 5 days.

Edge Cases

  • Start date is after the end date.
  • Start date and end date are the same.
  • The range covers multiple weekends and overlapping holidays.

Hints

Hint 1

Consider iterating through every day in the range or calculating the total week-days using math and then subtracting the holiday count.

Hint 2

Convert the input strings to datetime objects to easily extract the day of the week and perform date arithmetic.

Hint 3

Using a set for the holiday list allows for O(1) lookups when checking if a specific day is a holiday.

Follow-up questions

  • How would you optimize the solution if you needed to perform this calculation for thousands of different date ranges against the same holiday list?
  • What changes are required if the business week definition varies by region (e.g., Sunday to Thursday)?
  • How would you handle time zones if the input dates included timestamps instead of just days?