From 402c7d1e3f40174d46618d50ad75326b16047677 Mon Sep 17 00:00:00 2001
From: Slobodanvukojevic <slobodan2003@gmail.com>
Date: Tue, 19 Mar 2024 16:33:57 +0100
Subject: [PATCH 1/3] Added solutions 1-4

---
 .idea/.name                                   |  1 +
 .idea/gradle.xml                              | 16 ++++++++++++++++
 .idea/kotlinc.xml                             |  6 ++++++
 .idea/misc.xml                                |  5 +++++
 .idea/vcs.xml                                 |  6 ++++++
 .../exercise2/task1/FindPairOfHighestSum.kt   | 19 ++++++++++++++++++-
 .../task2/FindPairOfHighestSumFunctional.kt   |  2 +-
 .../ConvertMethodToFunctionalApproach.kt      |  6 +++---
 .../exercise2/task4/ProcessCountriesData.kt   | 16 ++++++++++------
 9 files changed, 66 insertions(+), 11 deletions(-)
 create mode 100644 .idea/.name
 create mode 100644 .idea/gradle.xml
 create mode 100644 .idea/kotlinc.xml
 create mode 100644 .idea/misc.xml
 create mode 100644 .idea/vcs.xml

diff --git a/.idea/.name b/.idea/.name
new file mode 100644
index 0000000..4cae352
--- /dev/null
+++ b/.idea/.name
@@ -0,0 +1 @@
+subject-kotlin-programming-language-exercises
\ No newline at end of file
diff --git a/.idea/gradle.xml b/.idea/gradle.xml
new file mode 100644
index 0000000..478f98e
--- /dev/null
+++ b/.idea/gradle.xml
@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="GradleSettings">
+    <option name="linkedExternalProjectsSettings">
+      <GradleProjectSettings>
+        <option name="externalProjectPath" value="$PROJECT_DIR$" />
+        <option name="gradleJvm" value="openjdk-21" />
+        <option name="modules">
+          <set>
+            <option value="$PROJECT_DIR$" />
+          </set>
+        </option>
+      </GradleProjectSettings>
+    </option>
+  </component>
+</project>
\ No newline at end of file
diff --git a/.idea/kotlinc.xml b/.idea/kotlinc.xml
new file mode 100644
index 0000000..8d81632
--- /dev/null
+++ b/.idea/kotlinc.xml
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="KotlinJpsPluginSettings">
+    <option name="version" value="1.9.22" />
+  </component>
+</project>
\ No newline at end of file
diff --git a/.idea/misc.xml b/.idea/misc.xml
new file mode 100644
index 0000000..53b7407
--- /dev/null
+++ b/.idea/misc.xml
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ExternalStorageConfigurationManager" enabled="true" />
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_17" project-jdk-name="11" project-jdk-type="JavaSDK" />
+</project>
\ No newline at end of file
diff --git a/.idea/vcs.xml b/.idea/vcs.xml
new file mode 100644
index 0000000..35eb1dd
--- /dev/null
+++ b/.idea/vcs.xml
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="" vcs="Git" />
+  </component>
+</project>
\ No newline at end of file
diff --git a/src/main/kotlin/exercise2/task1/FindPairOfHighestSum.kt b/src/main/kotlin/exercise2/task1/FindPairOfHighestSum.kt
index ddf425b..524f98b 100644
--- a/src/main/kotlin/exercise2/task1/FindPairOfHighestSum.kt
+++ b/src/main/kotlin/exercise2/task1/FindPairOfHighestSum.kt
@@ -18,7 +18,24 @@ import org.jetbrains.exercise2.task3.findPairWithBiggestDifference
  */
 
 internal fun List<Int>.findHighestSumPair(): Pair<Int, Int> {
-    TODO("Implement me!!")
+    var firstMaximal = this[0]
+    var maximalIndex = -1
+
+    for((index, num) in this.withIndex()) {
+        if(num > firstMaximal) {
+            firstMaximal = num
+            maximalIndex = index
+        }
+    }
+
+    var secondMaximal = this[0]
+    for((index, num) in this.withIndex()) {
+        if(num in (secondMaximal + 1)..firstMaximal && index != maximalIndex) {
+            secondMaximal = num
+        }
+    }
+
+    return firstMaximal to secondMaximal
 }
 
 fun main() {
diff --git a/src/main/kotlin/exercise2/task2/FindPairOfHighestSumFunctional.kt b/src/main/kotlin/exercise2/task2/FindPairOfHighestSumFunctional.kt
index b1527fa..4ae7050 100644
--- a/src/main/kotlin/exercise2/task2/FindPairOfHighestSumFunctional.kt
+++ b/src/main/kotlin/exercise2/task2/FindPairOfHighestSumFunctional.kt
@@ -20,7 +20,7 @@ import org.jetbrains.exercise2.task3.findPairWithBiggestDifference
  */
 
 internal fun List<Int>.findHighestSumPairFunctional(): Pair<Int, Int> {
-    TODO("Implement me!!")
+    return this.sortedDescending().let { it.first() to it[1] }
 }
 
 fun main() {
diff --git a/src/main/kotlin/exercise2/task3/ConvertMethodToFunctionalApproach.kt b/src/main/kotlin/exercise2/task3/ConvertMethodToFunctionalApproach.kt
index 47f814b..a379bd8 100644
--- a/src/main/kotlin/exercise2/task3/ConvertMethodToFunctionalApproach.kt
+++ b/src/main/kotlin/exercise2/task3/ConvertMethodToFunctionalApproach.kt
@@ -17,8 +17,8 @@ import kotlin.math.abs
  */
 
 internal fun List<Int>.findPairWithBiggestDifference(): Pair<Int, Int> {
-    // TODO refactor me to functional approach and make tests pass!!!
-    var resultPair: Pair<Int, Int>? = null
+    return this.sorted().let { it.first() to it.last() }
+    /*var resultPair: Pair<Int, Int>? = null
     var biggestDifference = Int.MIN_VALUE
 
     for (i in this.indices) {
@@ -34,7 +34,7 @@ internal fun List<Int>.findPairWithBiggestDifference(): Pair<Int, Int> {
         }
     }
 
-    return resultPair!!
+    return resultPair!!*/
 }
 
 fun main() {
diff --git a/src/main/kotlin/exercise2/task4/ProcessCountriesData.kt b/src/main/kotlin/exercise2/task4/ProcessCountriesData.kt
index 291e558..c1ae5f4 100644
--- a/src/main/kotlin/exercise2/task4/ProcessCountriesData.kt
+++ b/src/main/kotlin/exercise2/task4/ProcessCountriesData.kt
@@ -59,27 +59,31 @@ internal val countries = listOf(
  */
 
 internal fun List<Country>.findCountryWithBiggestTotalArea(): Country {
-    TODO("Implement me!!!")
+    return this.maxBy { it.totalAreaInSquareKilometers }
 }
 
 internal fun List<Country>.findCountryWithBiggestPopulation(): Country {
-    TODO("Implement me!!!")
+    return this.maxBy { it.population }
 }
 
 internal fun List<Country>.findCountryWithHighestPopulationDensity(): Country {
-    TODO("Implement me!!!")
+    return this.maxBy { it.population/it.totalAreaInSquareKilometers }
 }
 
 internal fun List<Country>.findCountryWithLowestPopulationDensity(): Country {
-    TODO("Implement me!!!")
+    return this.minBy { it.population / it.totalAreaInSquareKilometers }
 }
 
 internal fun List<Country>.findLanguageSpokenInMostCountries(): String {
-    TODO("Implement me!!!")
+    return this.flatMap { it.languages }
+        .groupingBy { it }
+        .eachCount()
+        .maxBy { it.value }
+        .key
 }
 
 internal fun List<Country>.filterCountriesThatSpeakLanguage(language: String): List<Country> {
-    TODO("Implement me!!!")
+    return this.filter { it.languages.contains(language) }
 }
 
 

From 8d0975b8fb0f7a5561b88b940a0a0fb889b75f7f Mon Sep 17 00:00:00 2001
From: Slobodanvukojevic <slobodan2003@gmail.com>
Date: Tue, 19 Mar 2024 16:44:34 +0100
Subject: [PATCH 2/3] Added solutions 1-4

---
 .idea/gradle.xml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.idea/gradle.xml b/.idea/gradle.xml
index 478f98e..622f299 100644
--- a/.idea/gradle.xml
+++ b/.idea/gradle.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
+  <component name="GradleMigrationSettings" migrationVersion="1" />
   <component name="GradleSettings">
     <option name="linkedExternalProjectsSettings">
       <GradleProjectSettings>

From 7646f8adcb4bc60300db2a4935fbb40ec6bf797a Mon Sep 17 00:00:00 2001
From: Slobodanvukojevic <slobodan2003@gmail.com>
Date: Sun, 31 Mar 2024 00:18:05 +0100
Subject: [PATCH 3/3] added tasks 1,2,4, I have no idea how to solve task 3

---
 .idea/misc.xml                                |  1 -
 .../exercise3/task1/BalancedBrackets.kt       | 20 +++++++++-
 .../exercise3/task2/ParenthesesClusters.kt    | 32 +++++++++++++++-
 .../kotlin/exercise3/task4/TaxiParkTask.kt    | 37 ++++++++++++++++---
 4 files changed, 82 insertions(+), 8 deletions(-)

diff --git a/.idea/misc.xml b/.idea/misc.xml
index 53b7407..2189e58 100644
--- a/.idea/misc.xml
+++ b/.idea/misc.xml
@@ -1,4 +1,3 @@
-<?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="ExternalStorageConfigurationManager" enabled="true" />
   <component name="ProjectRootManager" version="2" languageLevel="JDK_17" project-jdk-name="11" project-jdk-type="JavaSDK" />
diff --git a/src/main/kotlin/exercise3/task1/BalancedBrackets.kt b/src/main/kotlin/exercise3/task1/BalancedBrackets.kt
index 7a6958d..063a534 100644
--- a/src/main/kotlin/exercise3/task1/BalancedBrackets.kt
+++ b/src/main/kotlin/exercise3/task1/BalancedBrackets.kt
@@ -26,7 +26,25 @@ package exercise3.task1
 
 
 internal fun isExpressionBalanced(expression: String): Boolean {
-    TODO("Implement me!!!")
+    val stack = mutableListOf<Char>()
+
+    for (char in expression) {
+        when (char) {
+            '(', '{', '[' -> stack.add(char)
+            ')', '}', ']' -> {
+                if (stack.isEmpty()) return false
+                val last = stack.removeAt(stack.size - 1)
+                if ((char == ')' && last != '(') ||
+                    (char == '}' && last != '{') ||
+                    (char == ']' && last != '[')
+                ) {
+                    return false
+                }
+            }
+        }
+    }
+
+    return stack.isEmpty()
 }
 
 fun main() {
diff --git a/src/main/kotlin/exercise3/task2/ParenthesesClusters.kt b/src/main/kotlin/exercise3/task2/ParenthesesClusters.kt
index 0e75083..6854d0b 100644
--- a/src/main/kotlin/exercise3/task2/ParenthesesClusters.kt
+++ b/src/main/kotlin/exercise3/task2/ParenthesesClusters.kt
@@ -24,9 +24,39 @@ package exercise3.task2
  */
 
 internal fun String.splitToBracketsClusters(): List<String> {
-    TODO("Implement me!!!")
+    val stack = mutableListOf<Char>()
+    val clusters = mutableListOf<String>()
+    var currentCluster = ""
+
+    for (char in this) {
+        when (char) {
+            '(' -> {
+                stack.add(char)
+                currentCluster += char
+            }
+            ')' -> {
+                if (stack.isEmpty())
+                    return emptyList()
+                val last = stack.removeAt(stack.size - 1)
+                if (last == '(')
+                    currentCluster += char
+                else
+                    return emptyList()
+                if (stack.isEmpty()) {
+                    clusters.add(currentCluster)
+                    currentCluster = ""
+                }
+            }
+        }
+    }
+    if (stack.isNotEmpty())
+        return emptyList()
+
+    return clusters
+
 }
 
+
 fun main() {
     val expressionsToClustersCatalog = mapOf(
         "()()()" to listOf("()", "()", "()"),
diff --git a/src/main/kotlin/exercise3/task4/TaxiParkTask.kt b/src/main/kotlin/exercise3/task4/TaxiParkTask.kt
index 0dfe831..fe570d8 100755
--- a/src/main/kotlin/exercise3/task4/TaxiParkTask.kt
+++ b/src/main/kotlin/exercise3/task4/TaxiParkTask.kt
@@ -10,7 +10,8 @@ package exercise3.task4
  * Find all the drivers who performed no trips.
  */
 internal fun TaxiPark.findFakeDrivers(): Set<Driver> {
-    TODO("Implement me!!!")
+    return allDrivers.filter { driver -> trips.none { it.driver == driver } }
+        .toSet()
 }
 
 /**
@@ -18,15 +19,28 @@ internal fun TaxiPark.findFakeDrivers(): Set<Driver> {
  * Find all the clients who completed at least the given number of trips.
  */
 internal fun TaxiPark.findFaithfulPassengers(minTrips: Int): Set<Passenger> {
-    TODO("Implement me!!!")
-}
+    val passengerTripsCount = trips
+        .flatMap { it.passengers }
+        .groupingBy { it }
+        .eachCount()
+
+    return passengerTripsCount
+        .filter { it.value >= minTrips }
+        .keys}
 
 /**
  * Subtask 3:
  * Find all the passengers, who were taken by a given driver more than once.
  */
 internal fun TaxiPark.findFrequentPassengers(driver: Driver): Set<Passenger> {
-    TODO("Implement me!!!")
+    val frequentPassengers = trips
+        .filter { it.driver == driver }
+        .flatMap { it.passengers }
+        .groupingBy { it }
+        .eachCount()
+        .filter { it.value > 1 }
+
+    return frequentPassengers.keys
 }
 
 /**
@@ -34,5 +48,18 @@ internal fun TaxiPark.findFrequentPassengers(driver: Driver): Set<Passenger> {
  * Find the passengers who had a discount for the majority of their trips.
  */
 internal fun TaxiPark.findSmartPassengers(): Set<Passenger> {
-    TODO("Implement me!!!")
+    val passengerDiscountTripsCount = trips
+        .flatMap { trip ->
+            trip.passengers.map { passenger ->
+                passenger to (if (trip.discount != null && trip.discount > 0) 1 else 0)
+            }
+        }
+        .groupBy({ it.first }, { it.second })
+        .mapValues { (_, discounts) -> discounts.sum() }
+
+    return passengerDiscountTripsCount
+        .filter { (_, discounts) ->
+            discounts >= trips.size / 2
+        }
+        .keys
 }