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@mayonesa
Created February 6, 2022 22:35
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Time using at most 2 numbers
import java.text.SimpleDateFormat
import java.time.Instant
import java.util.Date
import java.util.concurrent.TimeUnit
import TimeUnit.{MILLISECONDS => Milliseconds}
import TimeUnit.{SECONDS => Seconds}
import scala.annotation.tailrec
/*
An interesting time is a local time string in the format of HH:mm:ss and using
only at most two numbers.
These are examples of interesting time:
- 00:00:00 // uses only 1 number, zero
- 02:02:20 // uses only 2 numbers, zero and two
- 11:12:22 // uses only 2 numbers, one and two
These are not examples of interesting time:
- 10:30:00 // uses zero, one and three
- 10:20:59 // uses zero, one, two, five and nine
Given two local time string in the format of HH:mm:ss (ex. "05:59:07") t1 and
t2, count all interesting time in between t1 and t2 including t1 and t2.
Correctness and not performance is the focus of the solution.
*/
object InterestingTimes {
private val InFormat = new SimpleDateFormat("HH:mm:ss")
private val NumbersOnly = new SimpleDateFormat("HHmmss")
def numberOfInterestingTimes(fromStr: String, toStr: String): Int = {
val from = InFormat.parse(fromStr)
val to = InFormat.parse(toStr)
val diffInSeconds = Seconds.convert(to.getTime - from.getTime, Milliseconds).toInt
(0 to diffInSeconds).foldLeft(0) { case (nInterestingTimes, secondIncrement) =>
val time = from.toInstant.plusSeconds(secondIncrement)
nInterestingTimes + (if (interesting(time)) 1 else 0)
}
}
private def interesting(time: Instant) = {
@tailrec
def loop(str: String, acc: Set[Char]): Boolean =
if (str.isEmpty) true
else {
val c = str.head
val newAcc = acc + c
if (newAcc.size > 2) false
else loop(str.tail, newAcc)
}
loop(NumbersOnly.format(Date.from(time)), Set())
}
}
import org.scalatest.flatspec.AnyFlatSpec
class InterestingTimesSpec extends AnyFlatSpec {
"no interest" should "0" in {
assert(InterestingTimes.numberOfInterestingTimes("10:30:00", "10:59:59") === 0)
}
"inclusive interest" should "be inclusive" in {
assert(InterestingTimes.numberOfInterestingTimes("10:00:00", "10:00:01") === 2)
}
"inside interest" should "be included" in {
assert(InterestingTimes.numberOfInterestingTimes("10:00:02", "10:00:12") === 2)
}
}
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