How should I practice Monthly Calendar with Custom Week Start?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Stripe phone screen problems in FastPrep.

Is Monthly Calendar with Custom Week Start associated with Stripe?

FastPrep tags this as a Stripe phone screen coding practice problem when the problem catalog has that company and stage context.

Monthly Calendar with Custom Week Start

Stripe● MediumINTERNPHONE SCREEN

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Problem statement

Given a year, a month, and a weekday startDay, return that month's calendar as an integer matrix.

Calendar conventions

For this exercise, assume the proleptic Gregorian calendar: apply the Gregorian rules to every supported year, including years before 1582.
A year is a leap year if it is divisible by 400, or if it is divisible by 4 and not divisible by 100. February has 29 days in a leap year and 28 otherwise. April, June, September, and November have 30 days; the other months have 31.
For this exercise, number weekdays as 0 = Sunday, 1 = Monday, 2 = Tuesday, 3 = Wednesday, 4 = Thursday, 5 = Friday, and 6 = Saturday.
The inputs are valid. You may compute weekdays using any correct method.

Calendar layout

Each row represents one week and contains exactly 7 cells.
The leftmost column is startDay. Each following column advances one weekday, wrapping from Saturday to Sunday.
Place the day numbers from 1 through the last day of the month in chronological order, under their corresponding weekdays.
For this exercise, fill cells before day 1 and after the month's last day with 0.
Return only weeks containing at least one day of the requested month. Do not add an all-zero row.

Progressive task

The calendar exercise builds through these steps:

Determine the weekday of a date.
Use the month's length to determine the weekday of its last day.
Build a month table with weekday 0 in the first column.
Generalize the first column to startDay.

Implement the final generalized calendar. The earlier steps can serve as helpers.

Function

buildMonthlyCalendar(year: int, month: int, startDay: int) → int[][]

Examples

Example 1

year = 2024month = 2startDay = 1return = [[0,0,0,1,2,3,4],[5,6,7,8,9,10,11],[12,13,14,15,16,17,18],[19,20,21,22,23,24,25],[26,27,28,29,0,0,0]]

February 2024 starts on Thursday and has 29 days. The columns are Monday through Sunday, so the first row begins with three zeros. The last row contains 26, 27, 28, 29 followed by three zeros.

Example 2

year = 2021month = 2startDay = 1return = [[1,2,3,4,5,6,7],[8,9,10,11,12,13,14],[15,16,17,18,19,20,21],[22,23,24,25,26,27,28]]

February 2021 starts on Monday and has 28 days. With Monday as the first column, the month fills exactly four weeks and needs no padding.

Example 3

year = 2026month = 8startDay = 0return = [[0,0,0,0,0,0,1],[2,3,4,5,6,7,8],[9,10,11,12,13,14,15],[16,17,18,19,20,21,22],[23,24,25,26,27,28,29],[30,31,0,0,0,0,0]]

August 2026 starts on Saturday. The first row has six zeros before 1. The final row begins with Sunday 30 and Monday 31, so six rows are required.

Constraints

For this exercise, assume 1 <= year <= 9999.
1 <= month <= 12.
0 <= startDay <= 6.