add mergesort

- add point sorter
- fix typo in BranchAndMerge

src/main/kotlin/it/norangeb/algorithms/exercises/BranchAndMerge.kt

@@ -37,10 +37,10 @@ class BranchAndMerge<T>(
     companion object {
         private const val TMP_FILE_PATH_1 = "/tmp/file1"
         private const val TMP_FILE_PATH_2 = "/tmp/file2"
+        private val GSON = Gson()
     }
-    private val GSON = Gson()
 
-    fun run(source: File) {
+    fun sort(source: File) {
         tryBranch(source)
 
         while (!isSorted()) {

src/main/kotlin/it/norangeb/algorithms/exercises/PointSorter.kt

@@ -0,0 +1,84 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2019 norangebit
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+
+package it.norangeb.algorithms.exercises
+
+import it.norangeb.algorithms.sorting.Mergesort
+
+data class Point(val x: Double, val y: Double) {
+
+    constructor(x: Int, y: Int) : this(x.toDouble(), y.toDouble())
+
+    operator fun minus(other: Point): Point {
+        val x = this.x - other.x
+        val y = this.y - other.y
+
+        return Point(x, y)
+    }
+
+    fun theta(): Double = Math.atan2(y, x)
+
+    companion object {
+        fun thetaComparator(
+            p1: Point,
+            p2: Point,
+            origin: Point = Point(0, 0)
+        ): Int {
+            var theta1 = (p1 - origin).theta()
+            var theta2 = (p2 - origin).theta()
+
+            if (theta1 < 0) theta1 += 2 * Math.PI
+            if (theta2 < 0) theta2 += 2 * Math.PI
+
+            return theta1.compareTo(theta2)
+        }
+    }
+}
+
+typealias P = Point
+
+fun main(args: Array<String>) {
+    if (args.size < 4 || args.size % 2 != 0) return
+
+    val origin = P(args[0].toDouble(), args[1].toDouble())
+
+    val list = ArrayList<Point>()
+
+    for (i in 2 until args.size step 2)
+        list.add(P(args[i].toDouble(), args[i + 1].toDouble()))
+
+    val points = list.toTypedArray()
+
+    val compare = { p1: Point, p2: Point ->
+        Point.thetaComparator(p1, p2, origin)
+    }
+
+    Mergesort.sortWith(points, compare)
+
+    println("origin in $origin")
+    points.forEach {
+        println(it)
+    }
+}

src/main/kotlin/it/norangeb/algorithms/sorting/Mergesort.kt

@@ -0,0 +1,88 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2019 norangebit
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+
+package it.norangeb.algorithms.sorting
+
+object Mergesort : Sorter {
+    override fun <T : Comparable<T>> sort(array: Array<T>) {
+        sort(array) { t1, t2 -> t1 < t2 }
+    }
+
+    override fun <T, C : Comparable<C>> sortBy(array: Array<T>, compareBy: (T) -> C) {
+        sort(array) { t1, t2 -> compareBy(t1) < compareBy(t2) }
+    }
+
+    override fun <T> sortWith(array: Array<T>, compare: (T, T) -> Int) {
+        sort(array) { t1, t2 -> compare(t1, t2) < 0 }
+    }
+
+    private fun <T> sort(array: Array<T>, isLess: (T, T) -> Boolean) {
+        val auxiliary = arrayOfNulls<Any>(array.size) as Array<T>
+        sort(array, auxiliary, 0, array.size - 1, isLess)
+    }
+
+    private fun <T> sort(
+        array: Array<T>,
+        auxiliary: Array<T>,
+        low: Int,
+        high: Int,
+        isLess: (T, T) -> Boolean
+    ) {
+        if (high <= low) return
+
+        val mid = low + (high - low) / 2
+
+        sort(array, auxiliary, low, mid, isLess)
+        sort(array, auxiliary, mid + 1, high, isLess)
+
+        if (!isLess(array[mid+1], array[mid]))
+            return
+
+        merge(array, auxiliary, low, mid, high, isLess)
+    }
+
+    private inline fun <T> merge(
+        array: Array<T>,
+        auxiliary: Array<T>,
+        low: Int,
+        mid: Int,
+        high: Int,
+        isLess: (T, T) -> Boolean
+    ) {
+        for (i in low..high)
+            auxiliary[i] = array[i]
+
+        var i = low
+        var j = mid + 1
+
+        for (k in low..high)
+            when {
+                i > mid -> array[k] = auxiliary[j++]
+                j > high -> array[k] = auxiliary[i++]
+                isLess(auxiliary[j], auxiliary[i]) -> array[k] = auxiliary[j++]
+                else -> array[k] = auxiliary[i++]
+            }
+    }
+}

src/main/kotlin/it/norangeb/algorithms/sorting/Sorter.kt

@@ -0,0 +1,32 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2019 norangebit
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+
+package it.norangeb.algorithms.sorting
+
+interface Sorter {
+    fun <T : Comparable<T>> sort(array: Array<T>)
+    fun <T, C : Comparable<C>> sortBy(array: Array<T>, compareBy: (T) -> C)
+    fun <T> sortWith(array: Array<T>, compare: (T, T) -> Int)
+}

src/test/kotlin/it/norangeb/algorithms/exercises/BranchAndMergeTest.kt

@@ -281,7 +281,7 @@ class BranchAndMergeTest {
         ps.close()
 
         BranchAndMerge(Int::class.java, this::defaultComparator)
-            .run(File(filePath))
+            .sort(File(filePath))
 
         File(filePath).readLines()
             .map { it.toInt() } `should equal` testSet
@@ -297,7 +297,7 @@ class BranchAndMergeTest {
         ps.close()
 
         BranchAndMerge(Int::class.java, this::defaultComparator)
-            .run(File(filePath))
+            .sort(File(filePath))
 
         File(filePath).readLines()
             .map { it.toInt() } `should equal` testSet.sorted()
@@ -313,7 +313,7 @@ class BranchAndMergeTest {
         ps.close()
 
         BranchAndMerge(Int::class.java) { it1, it2 -> it2.compareTo(it1) }
-            .run(File(filePath))
+            .sort(File(filePath))
 
         File(filePath).readLines()
             .map { it.toInt() } `should equal` testSet.sorted().reversed()
@@ -343,7 +343,7 @@ class BranchAndMergeTest {
         }
 
         BranchAndMerge(Person::class.java, sortByAge)
-            .run(File(filePath))
+            .sort(File(filePath))
 
         File(filePath).readLines()
             .map { gson.fromJson(it, Person::class.java) } `should equal`

src/test/kotlin/it/norangeb/algorithms/sorting/MergesortTest.kt

@@ -0,0 +1,90 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2019 norangebit
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+
+package it.norangeb.algorithms.sorting
+
+import org.amshove.kluent.`should equal`
+import org.junit.jupiter.api.Test
+import kotlin.reflect.full.memberFunctions
+import kotlin.reflect.jvm.isAccessible
+
+class MergesortTest {
+
+    @Test
+    fun testMerge() {
+        val merge = Mergesort::class.memberFunctions
+            .find { it.name == "merge" }
+            .also { it?.isAccessible = true }
+
+        val array = arrayOf(3, 7, 9, 12, 1, 4, 6, 10)
+        val low = 0
+        val mid = 3
+        val high = array.size - 1
+        val auxiliary = arrayOfNulls<Int>(array.size)
+
+        merge?.call(
+            Mergesort,
+            array,
+            auxiliary,
+            low,
+            mid,
+            high,
+            { int1: Int, int2: Int ->
+                int1 < int2
+            }
+        )
+
+        array `should equal` array.sortedArray()
+    }
+
+    @Test
+    fun testSort() {
+        val array = arrayOf(5, 2, 3, 1, 4)
+
+        Mergesort.sort(array)
+
+        array `should equal` array.sortedArray()
+    }
+
+    @Test
+    fun testSortBy() {
+        val array = arrayOf(5, 2, 1, 4, 3)
+
+        Mergesort.sortBy(array) { it }
+
+        array `should equal` array.sortedArray()
+    }
+
+    @Test
+    fun testSortWith() {
+        val array = arrayOf(4, 5, 3, 2, 1)
+
+        Mergesort.sortWith(array) { t1, t2 ->
+            t1.compareTo(t2)
+        }
+
+        array `should equal` array.sortedArray()
+    }
+}