Find all nearest date from list of date in kotlin - kotlin

Question

I have current date and I have of list which is coming from server. I want to find all first nearest data.
"Results": [
{
"date": "May 9, 2020 8:09:03 PM",
"id": 1
},
{
"date": "Apr 14, 2020 8:09:03 PM",
"id": 2
},
{
"date": "Mar 15, 2020 8:09:03 PM",
"id": 3
},
{
"date": "May 9, 2020 8:19:03 PM",
"id": 4
}
],
Today date is Wed Jul 20 00:00:00 GMT+01:00 2022 I am getting through this my own StackOverflow. Inside this SO I am taking current date.
Expected Output
[Result(date=May 9, 2020 8:09:03 PM, id = 1), Result(date=May 9, 2020 8:19:03 PM, id = 4)]
So How can I do in idiomatic way in kotlin ?

Answer 1

There are quite a few ways this question could be solved with, ranging from simple to moderately complex depending on requirements such as efficiency. With some assumptions, below is a linear-time solution that is decently idiomatic and is only 3 lines in essence.
import kotlin.math.abs
import java.lang.Long.MAX_VALUE
import java.time.LocalDateTime
import java.time.temporal.ChronoUnit
import java.time.temporal.Temporal
data class Result(val date: LocalDateTime, val id: Int)
fun getClosestDays(toDate: Temporal, results: List<Result>): List<Result> {
// Find the minimum amount of days to the current date
var minimumDayCount = MAX_VALUE
results.forEach { minimumDayCount = minOf(minimumDayCount, abs(ChronoUnit.DAYS.between(toDate, it.date))) }
// Grab all results that match the minimum day count
return results.filter { abs(ChronoUnit.DAYS.between(toDate, it.date)) == minimumDayCount }
}
fun main() {
getClosestDays(
LocalDateTime.now(),
listOf(
Result(LocalDateTime.of(2020, 5, 9, 8, 9, 3), 1),
Result(LocalDateTime.of(2020, 4, 14, 8, 9, 3), 2),
Result(LocalDateTime.of(2020, 3, 15, 8, 9, 3), 3),
Result(LocalDateTime.of(2020, 5, 9, 8, 19, 3), 4)
)
).also { println(it) }
}
Here is the output:
[Result(date=2020-05-09T08:09:03, id=1), Result(date=2020-05-09T08:19:03, id=4)]
And here you can play with it yourself.