add UE09_Rekursion2

src/UE09_191124_Rekursion2/UE09_Rekursion2.java

@@ -0,0 +1,57 @@
+package UE09_191124_Rekursion2;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+
+public class UE09_Rekursion2 {
+    public static void main(String[] args) {
+//        int[][] file1 = readFile("src/UE09_191124_Rekursion2/UE09_triangle1.txt");
+//        int[][] file2 = readFile("src/UE09_191124_Rekursion2/UE09_triangle2.txt");
+//        int[][] file3 = readFile("src/UE09_191124_Rekursion2/UE09_triangle.txt");
+//        System.out.println("\n" + maxTotalRekursion(file1, 0, 0));
+//        System.out.println("\n" + maxTotalRekursion(file2, 0, 0));
+//        System.out.println("\n" + maxTotalRekursion(file3, 0, 0)); //Braucht ewig lange, da File sehr groß
+        System.out.println(collatz());
+    }
+
+    public static int[][] readFile(String file) {
+        try {
+            List<String> lines = Files.readAllLines(Path.of(file));
+            int[][] output = new int[lines.size()][];
+            for (int i = 0; i < output.length; i++) {
+                String[] line = lines.get(i).trim().split(" ");
+                output[i] = new int[line.length];
+                for (int j = 0; j < line.length; j++) output[i][j] = Integer.parseInt(line[j]);
+            }
+            return output;
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public static long maxTotalRekursion(int[][] input, int x, int y) {
+        return (x >= input.length - 1) ? input[x][y] : Long.max(maxTotalRekursion(input, x + 1, y), maxTotalRekursion(input, x + 1, y + 1)) + input[x][y];
+    }
+
+    public static long collatz() {
+        long startingNumber = 0, maxLength = 0;
+        for (int i = 1; i < 1000000; i++) {
+            long length = longestCollatzSequence(new ArrayList<>(), i).size();
+            if (length > maxLength) {
+                maxLength = length;
+                startingNumber = i;
+            }
+        }
+        return startingNumber;
+    }
+
+    public static List<Long> longestCollatzSequence(List<Long> l, long n) {
+        if (n == 1) return l;
+        l.add(n);
+        n = ((n & 1) == 0) ? (n / 2) : (3 * n + 1);
+        return longestCollatzSequence(l, n);
+    }
+}