Wednesday, July 15

phantom-day

daily challenge12

today's brief

Open any spreadsheet and type the date February 29, 1900. Excel says it exists. It never did: 1900 was not a leap year, because a century is a leap year only when it divides by 400. Microsoft kept the phantom day on purpose, back in 1985, to stay compatible with Lotus 1-2-3, and it is still sitting in every copy of Excel today. Your job is the honest rule, with no day that never happened.

Repair this code

Repair the leap-year rule so a century year counts as leap only when it is divisible by 400.

Steps

feb_days returns 29 in a leap year and 28 otherwise.
A year is a leap year when it is divisible by 4, except centuries, which must also be divisible by 400.
So 1900 and 2100 have 28 days in February, but 2000 has 29.
Fix the rule in the starter, which wrongly treats every divisible-by-4 year as leap.

examples

$ feb_days(1900)

$ feb_days(2000)

$ feb_days(2024)

Constraints

Expected files

leap.c

Allowed functions

None. Write every helper yourself.

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Solutions

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