Added obligatory assignments

src/assignment/week3/taxipark/TaxiParkTask.kt

@@ -0,0 +1,80 @@
+package taxipark
+
+/*
+ * Task #1. Find all the drivers who performed no trips.
+ */
+fun TaxiPark.findFakeDrivers(): Set<Driver> =
+    this.allDrivers
+        .filter { driver -> this.trips.none { trip -> trip.driver == driver } }
+        .toSet()
+
+/*
+ * Task #2. Find all the clients who completed at least the given number of trips.
+ */
+fun TaxiPark.findFaithfulPassengers(minTrips: Int): Set<Passenger> =
+    this.allPassengers
+        .filter { passenger -> this.trips.count { trip -> trip.passengers.contains(passenger) } >= minTrips }
+        .toSet()
+
+/*
+ * Task #3. Find all the passengers, who were taken by a given driver more than once.
+ */
+fun TaxiPark.findFrequentPassengers(driver: Driver): Set<Passenger> =
+    this.allPassengers
+        .filter { passenger ->
+            this.trips
+                .filter { trip -> trip.passengers.contains(passenger) }
+                .count { trip -> trip.driver == driver } > 1
+        }
+        .toSet()
+
+/*
+ * Task #4. Find the passengers who had a discount for majority of their trips.
+ */
+fun TaxiPark.findSmartPassengers(): Set<Passenger> = this.allPassengers
+    .filter(fun(passenger: Passenger): Boolean {
+        val (discounted, nonDiscounted) = this.trips
+            .filter { it.passengers.contains(passenger) }
+            .partition { it.discount != null }
+
+        if (nonDiscounted.isEmpty()) {
+            return discounted.isNotEmpty()
+        }
+        return (discounted.size.toDouble()) / nonDiscounted.size > 1.0
+    })
+    .toSet()
+
+/*
+ * Task #5. Find the most frequent trip duration among minute periods 0..9, 10..19, 20..29, and so on.
+ * Return any period if many are the most frequent, return `null` if there're no trips.
+ */
+fun TaxiPark.findTheMostFrequentTripDurationPeriod(): IntRange? {
+    val maxDuration = this.trips
+        .map { trip -> trip.duration / 10 }
+        .groupBy { it }
+        .maxByOrNull { it.value.size }
+
+    val startRange = maxDuration?.let { it.key * 10 }
+    return startRange?.let { it.rangeTo(it + 9) }
+}
+
+/*
+ * Task #6.
+ * Check whether 20% of the drivers contribute 80% of the income.
+ */
+fun TaxiPark.checkParetoPrinciple(): Boolean {
+    if (this.trips.isEmpty()) {
+        return false
+    }
+    val totalIncome = this.trips.sumOf(Trip::cost)
+
+    val top20Percent = this.trips
+        .groupBy { it.driver }
+        .values
+        .map { trips -> trips.sumOf(Trip::cost) }
+        .sortedDescending()
+        .take((this.allDrivers.size * 0.2).toInt())
+        .sum()
+
+    return top20Percent >= totalIncome * 0.8
+}