Finish both AmicableNumbers and VampireNumbers

BenSchokoRiegel · BenSchokoRiegel · commit e59fc81075ca · 2020-05-05T00:13:08.000+02:00
diff --git a/Maths/VampireNumber.java b/Maths/VampireNumber.java
@@ -0,0 +1,94 @@
+package Maths;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+/**
+ n number theory, a vampire number (or true vampire number) is a composite natural number with an even number of digits,
+ that can be factored into two natural numbers each with half as many digits as the original number
+ and not both with trailing zeroes, where the two factors contain precisely
+ all the digits of the original number, in any order, counting multiplicity.
+ The first vampire number is 1260 = 21 × 60.
+ * *
+ * <p>
+ * * link: https://en.wikipedia.org/wiki/Vampire_number
+ * * </p>
+ * <p>
+ *
+ */
+
+
+
+
+
+
+
+public class VampireNumber {
+
+    public static void main(String[] args) {
+
+      test(10,1000);
+    }
+
+     static void  test(int  startValue,  int  stopValue) {
+         int countofRes = 1;
+         StringBuilder res = new StringBuilder();
+
+
+         for (int i = startValue; i <= stopValue; i++) {
+             for (int j = i; j <= stopValue; j++) {
+                 // System.out.println(i+ " "+ j);
+                 if (isVampireNumber(i, j,true)) {
+                     countofRes++;
+                     res.append("" + countofRes + ": = ( " + i + "," + j + " = " + i*j + ")" + "\n");
+                 }
+             }
+         }
+         System.out.println(res);
+     }
+
+
+
+
+        static boolean isVampireNumber(int a, int b, boolean noPseudoVamireNumbers ) {
+
+        // this is for pseudoVampireNumbers  pseudovampire number need not be of length n/2 digits for example
+            // 126 = 6 x 21
+            if (noPseudoVamireNumbers) {
+                if (a * 10 <= b || b * 10 <= a) {
+                    return false;
+                }
+            }
+
+            String mulDigits = splitIntoDigits(a*b,0);
+             String faktorDigits = splitIntoDigits(a,b);
+
+            return mulDigits.equals(faktorDigits);
+            }
+
+
+
+// methode to Split the numbers to Digits
+        static String splitIntoDigits(int num, int num2) {
+
+        StringBuilder res = new StringBuilder();
+
+            ArrayList<Integer> digits = new ArrayList<>();
+            while (num > 0) {
+                digits.add(num%10);
+                num /= 10;
+            }
+            while (num2 > 0) {
+                digits.add(num2%10);
+                num2/= 10;
+            }
+            Collections.sort(digits);
+            for (int i : digits) {
+                res.append(i);
+            }
+
+
+            return res.toString();
+        }
+}
