Refactor assignment 3 and implement alternative Pareto Principle

src/assignment/week3/nicestring/NiceString.kt

@@ -1,25 +1,22 @@
-package nicestring
+package assignment.week3.nicestring
 
-fun String.isNice(): Boolean {
-    return listOf(
-        ::containsNotNiceSubstring,
-        ::containsAtLeastThreeVowels,
-        ::containsDoubleLetter
-    )
-        .count { it() } >= 2
-}
+const val VOWELS = "aeiou"
 
-fun String.containsNotNiceSubstring(): Boolean {
+fun String.isNice(): Boolean = listOf(
+    ::containsNotNiceSubstring,
+    ::containsAtLeastThreeVowels,
+    ::containsDoubleLetter
+).count { it() } >= 2
+
+private fun String.containsNotNiceSubstring(): Boolean {
     val illegalSubStrings = listOf("bu", "ba", "be")
     return this.zipWithNext()
         .map { (first, second) -> "$first$second" }
         .none { it in illegalSubStrings }
 }
 
-fun String.containsAtLeastThreeVowels(): Boolean {
-    val vovels = "aeiou".toCharArray()
-    return this.count { char -> char in vovels } >= 3
-}
+private fun String.containsAtLeastThreeVowels(): Boolean =
+    this.count { char -> char in VOWELS.toCharArray() } >= 3
 
-fun String.containsDoubleLetter(): Boolean = this.zipWithNext()
+private fun String.containsDoubleLetter(): Boolean = this.zipWithNext()
     .any { (first, second) -> first == second }

src/assignment/week3/taxipark/TaxiPark.kt

@@ -1,22 +1,23 @@
-package taxipark
+package assignment.week3.taxipark
 
 data class TaxiPark(
-        val allDrivers: Set<Driver>,
-        val allPassengers: Set<Passenger>,
-        val trips: List<Trip>)
+    val allDrivers: Set<Driver>,
+    val allPassengers: Set<Passenger>,
+    val trips: List<Trip>
+)
 
 data class Driver(val name: String)
 data class Passenger(val name: String)
 
 data class Trip(
-        val driver: Driver,
-        val passengers: Set<Passenger>,
-        // the trip duration in minutes
-        val duration: Int,
-        // the trip distance in km
-        val distance: Double,
-        // the percentage of discount (in 0.0..1.0 if not null)
-        val discount: Double? = null
+    val driver: Driver,
+    val passengers: Set<Passenger>,
+    // the trip duration in minutes
+    val duration: Int,
+    // the trip distance in km
+    val distance: Double,
+    // the percentage of discount (in 0.0..1.0 if not null)
+    val discount: Double? = null
 ) {
     // the total cost of the trip
     val cost: Double

src/assignment/week3/taxipark/TaxiParkParetoPrinciple.kt

@@ -0,0 +1,67 @@
+package assignment.week3.taxipark
+
+fun TaxiPark.checkParetoPrinciple2(): Boolean {
+    if (trips.isEmpty()) return false
+
+    val totalIncome = trips.sumOf { trip -> trip.cost }
+    val sortedDriversIncome: List<Double> = trips
+        .groupBy { it.driver }
+        .map { (_, tripsByDriver) -> tripsByDriver.sumOf { trip -> trip.cost } }
+        .sortedDescending()
+
+    val numberOfTopDrivers = (0.2 * allDrivers.size).toInt()
+    val incomeByTopDrivers = sortedDriversIncome
+        .take(numberOfTopDrivers)
+        .sum()
+
+    return incomeByTopDrivers >= 0.8 * totalIncome
+}
+
+fun main() {
+    taxiPark(
+        1..5, 1..4,
+        trip(1, 1, 20, 20.0),
+        trip(1, 2, 20, 20.0),
+        trip(1, 3, 20, 20.0),
+        trip(1, 4, 20, 20.0),
+        trip(2, 1, 20, 19.0)
+    )
+        .checkParetoPrinciple() eq true
+
+    taxiPark(
+        1..5, 1..4,
+        trip(1, 1, 20, 20.0),
+        trip(1, 2, 20, 20.0),
+        trip(1, 3, 20, 20.0),
+        trip(1, 4, 20, 20.0),
+        trip(2, 1, 20, 21.0)
+    )
+        .checkParetoPrinciple2() eq false
+}
+
+private infix fun <T> T.eq(other: T) {
+    if (this != other) throw AssertionError("Expected $this to equal $other")
+    println("OK")
+}
+
+private fun taxiPark(
+    allDrivers: IntProgression,
+    allPassengers: IntProgression,
+    vararg trips: Trip
+) = TaxiPark(
+    allDrivers = allDrivers.map { Driver(it.toString()) }.toSet(),
+    allPassengers = allPassengers.map { Passenger(it.toString()) }.toSet(),
+    trips = trips.toList()
+)
+
+private fun trip(
+    driver: Int,
+    passenger: Int,
+    duration: Int,
+    distance: Double
+) = Trip(
+    driver = Driver(driver.toString()),
+    passengers = setOf(Passenger(passenger.toString())),
+    duration = duration,
+    distance = distance
+)

src/assignment/week3/taxipark/TaxiParkTask.kt

@@ -1,4 +1,4 @@
-package taxipark
+package assignment.week3.taxipark
 
 /*
  * Task #1. Find all the drivers who performed no trips.
@@ -49,13 +49,13 @@ fun TaxiPark.findSmartPassengers(): Set<Passenger> = this.allPassengers
  * Return any period if many are the most frequent, return `null` if there're no trips.
  */
 fun TaxiPark.findTheMostFrequentTripDurationPeriod(): IntRange? {
-    val maxDuration = this.trips
+    val (maxDuration, _) = this.trips
         .map { trip -> trip.duration / 10 }
         .groupBy { it }
-        .maxByOrNull { it.value.size }
+        .maxByOrNull { it.value.size } ?: return null
 
-    val startRange = maxDuration?.let { it.key * 10 }
-    return startRange?.let { it.rangeTo(it + 9) }
+    val startRange = maxDuration * 10
+    return startRange.rangeTo(startRange + 9)
 }
 
 /*