Educational implementation of PowerSort

.idea/gradle.xml

@@ -5,7 +5,6 @@
     <option name="linkedExternalProjectsSettings">
       <GradleProjectSettings>
         <option name="externalProjectPath" value="$PROJECT_DIR$" />
-        <option name="gradleJvm" value="23" />
         <option name="modules">
           <set>
             <option value="$PROJECT_DIR$" />

app/src/main/java/de/uni_marburg/powersort/FinnSort/FinnSort.java

@@ -0,0 +1,112 @@
+package de.uni_marburg.powersort.FinnSort;
+import java.util.*;
+
+import static java.lang.Math.*;
+
+public class FinnSort {
+
+    private static final ArrayList<Run> runs = new ArrayList<>();
+
+    static void sort(Integer[] a) {
+
+        int n = a.length;
+        int i = 0;
+        int j = extendRunRight(a, i);
+
+        printList(a);
+
+        runs.add(new Run(i, j, 0));
+
+        i = j;
+        while (i < n) {
+            j = extendRunRight(a, i);
+
+            //printRuns();
+
+            int p = power(runs.getLast(), new Run(i, j, 0), n);
+
+            while (runs.size() >= 2 && p < power(runs.getLast(), runs.get(runs.size() - 2), n)) {
+                basicMerge(a, runs.removeFirst(), runs.removeFirst());
+            }
+
+            runs.add(new Run(i, j, p));
+            i = j;
+        }
+        while (runs.size() >= 2) {
+            basicMerge(a, runs.removeFirst(), runs.removeFirst());
+        }
+    }
+
+    private static void basicMerge(Integer[] a, Run r1, Run r2) {
+        ArrayList<Integer> run1 = new ArrayList<>(Arrays.asList(a).subList(r1.start, r1.end));
+        ArrayList<Integer> run2 = new ArrayList<>(Arrays.asList(a).subList(r2.start, r2.end));
+        ArrayList<Integer> merge = new ArrayList<>();
+
+        while (!run1.isEmpty() || !run2.isEmpty()) {
+            if (run2.isEmpty() || !run1.isEmpty() && run1.getFirst() < run2.getFirst()) {
+                merge.add(run1.removeFirst());
+            } else {
+                merge.add(run2.removeFirst());
+            }
+        }
+
+        System.arraycopy(merge.toArray(), 0, a, min(r1.start, r2.start), merge.size());
+        Run r = new Run(min(r1.start, r2.start), max(r1.end, r2.end), min(r1.power, r2.power));
+        runs.add(r);
+        printList(a);
+    }
+
+    private static int extendRunRight(Integer[] a, int i) {
+        int j = i + 1;
+        while (j < a.length && a[j-1] <= a[j]) {
+            j++;
+        }
+        return j;
+    }
+
+    private static int power(Run run1, Run run2, int n) {
+        if (run1.start == 0) {
+            return 0;
+        }
+        int n_1 = run1.end - run1.start;
+        int n_2 = run2.end - run2.start;
+        double a = ((double) run1.start + 0.5 * n_1 - 1) / n;
+        double b = ((double) run2.start + 0.5 * n_2 - 1) / n;
+        int l = 0;
+        while ((int) (a * pow(2, l)) == (int) (b * pow(2 ,l))) {
+            l++;
+        }
+        return l;
+    }
+
+    public static void printRuns() {
+        String s = "";
+        for (Run run : runs) {
+            s += "(" + run.start + " - " + run.end + ", p: " + run.power + ") ";
+        }
+        System.out.println(s);
+    }
+    public static void printList(Integer[] arr) {
+        String s = "";
+        int i = 0;
+        while (i < arr.length) {
+            String run = "[";
+            int j = extendRunRight(arr, i);
+            for (int t = i; t < j; t++) {
+                run += arr[t] + ", ";
+            }
+            s += run.substring(0, run.length()-2) +"]";
+            i = j;
+        }
+        System.out.println(s);
+    }
+
+    public static void main(String[] args) {
+        Integer[] numbers = new Integer[]{24, 25, 26, 27, 28, 21, 22, 23, 18, 19, 20, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 3, 1, 2};
+
+
+        sort(numbers);
+        System.out.println("Result: ");
+        System.out.println(new ArrayList<>(List.of(numbers)));
+    }
+}

app/src/main/java/de/uni_marburg/powersort/FinnSort/Run.java

@@ -0,0 +1,14 @@
+package de.uni_marburg.powersort.FinnSort;
+
+class Run {
+    int start;
+    int end;
+    int power;
+
+    public Run(int i, int j, int p) {
+        start = i;
+        end = j;
+        power = p;
+    }
+
+}