Given a year, report if it is a leap year.
The tricky thing here is that a leap year in the Gregorian calendar occurs:
on every year that is evenly divisible by 4
except every year that is evenly divisible by 100
unless the year is also evenly divisible by 400
For example, 1997 is not a leap year, but 1996 is. 1900 is not a leap year, but 2000 is.
If your language provides a method in the standard library that does this look-up, pretend it doesn't exist and implement it yourself.
Though our exercise adopts some very simple rules, there is more to learn!
For a delightful, four minute explanation of the whole leap year phenomenon, go watch this youtube video.
You will see a cases_test.go
file in this exercise. This holds the test
cases used in the leap_test.go
. You can mostly ignore this file.
However, if you are interested... we sometimes generate the test data from a
cross language repository. In that repo
exercises may have a .json file that
contains common test data. Some of our local exercises have an
intermediary program that takes the problem specification
JSON and turns in into Go structs that are fed into the <exercise>_test.go
file. The Go specific transformation of that data lives in the cases_test.go
file.
To run the tests run the command go test
from within the exercise directory.
If the test suite contains benchmarks, you can run these with the --bench
and --benchmem
flags:
go test -v --bench . --benchmem
Keep in mind that each reviewer will run benchmarks on a different machine, with different specs, so the results from these benchmark tests may vary.
For more detailed information about the Go track, including how to get help if you're having trouble, please visit the exercism.io Go language page.
JavaRanch Cattle Drive, exercise 3 http://www.javaranch.com/leap.jsp
It's possible to submit an incomplete solution so you can see how others have completed the exercise.
package leap
// Source: exercism/problem-specifications
// Commit: 18875ec Leap: Improve the specification so that code generation is more readable - … (#1468)
// Problem Specifications Version: 1.5.1
var testCases = []struct {
year int
expected bool
description string
}{
{2015, false, "year not divisible by 4 in common year"},
{1970, false, "year divisible by 2, not divisible by 4 in common year"},
{1996, true, "year divisible by 4, not divisible by 100 in leap year"},
{2100, false, "year divisible by 100, not divisible by 400 in common year"},
{2000, true, "year divisible by 400 in leap year"},
{1800, false, "year divisible by 200, not divisible by 400 in common year"},
}
package leap
import "testing"
func TestLeapYears(t *testing.T) {
for _, test := range testCases {
observed := IsLeapYear(test.year)
if observed != test.expected {
t.Fatalf("IsLeapYear(%d) = %t, want %t (%s)",
test.year, observed, test.expected, test.description)
}
}
}
// Benchmark 400 year interval to get fair weighting of different years.
func Benchmark400(b *testing.B) {
for i := 0; i < b.N; i++ {
for y := 1600; y < 2000; y++ {
IsLeapYear(y)
}
}
}
package leap
// IsLeapYear reports if a year is a leap year.
func IsLeapYear(year int) bool {
if year%400 == 0 {
return true
}
if year%4 == 0 && !(year%100 == 0) {
return true
}
return false
}
A huge amount can be learned from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.
Here are some questions to help you reflect on this solution and learn the most from it.
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