Data commit

Task/Vampire-number/Java/vampire-number-1.java

@@ -0,0 +1,48 @@
+import java.util.Arrays;
+import java.util.HashSet;
+
+public class VampireNumbers{
+    private static int numDigits(long num){
+        return Long.toString(Math.abs(num)).length();
+    }
+
+    private static boolean fangCheck(long orig, long fang1, long fang2){
+        if(Long.toString(fang1).endsWith("0") && Long.toString(fang2).endsWith("0")) return false;
+
+        int origLen = numDigits(orig);
+        if(numDigits(fang1) != origLen / 2 || numDigits(fang2) != origLen / 2) return false;
+
+        byte[] origBytes = Long.toString(orig).getBytes();
+        byte[] fangBytes = (Long.toString(fang1) + Long.toString(fang2)).getBytes();
+        Arrays.sort(origBytes);
+        Arrays.sort(fangBytes);
+        return Arrays.equals(origBytes, fangBytes);
+    }
+
+    public static void main(String[] args){
+        HashSet<Long> vamps = new HashSet<Long>();
+        for(long i = 10; vamps.size() <= 25; i++ ){
+            if((numDigits(i) % 2) != 0) {i = i * 10 - 1; continue;}
+            for(long fang1 = 2; fang1 <= Math.sqrt(i) + 1; fang1++){
+                if(i % fang1 == 0){
+                    long fang2 = i / fang1;
+                    if(fangCheck(i, fang1, fang2) && fang1 <= fang2){
+                        vamps.add(i);
+                        System.out.println(i + ": [" + fang1 + ", " + fang2 +"]");
+                    }
+                }
+            }
+        }
+        Long[] nums = {16758243290880L, 24959017348650L, 14593825548650L};
+        for(Long i : nums){
+            for(long fang1 = 2; fang1 <= Math.sqrt(i) + 1; fang1++){
+                if(i % fang1 == 0){
+                    long fang2 = i / fang1;
+                    if(fangCheck(i, fang1, fang2) && fang1 <= fang2){
+                        System.out.println(i + ": [" + fang1 + ", " + fang2 +"]");
+                    }
+                }
+            }
+        }
+    }
+}

Task/Vampire-number/Java/vampire-number-2.java

@@ -0,0 +1,70 @@
+public class VampireNumber {
+
+    public static void main(String args[]) {
+
+        // scan only the ranges that have an even number of digits
+        // for instance: 10 .. 99, 1000 .. 9999 etc
+        long countVamps = 0, start = 10, tens = 10;
+        outer:
+        for (int numDigits = 2; numDigits <= 18; numDigits += 2) {
+            long end = start * 10;
+            for (long i = start; i < end; i++) {
+                if (countFangs(i, tens) > 0) {
+                    if (++countVamps >= 26)
+                        break outer;
+                }
+            }
+            start *= 100;
+            tens *= 10;
+        }
+        System.out.println();
+
+        long[] bigs = {16758243290880L, 24959017348650L,
+            14593825548650L};
+
+        for (long b : bigs)
+            countFangs(b, 10000000L);
+    }
+
+    private static int countFangs(long n, long tens) {
+        int countFangs = 0;
+
+        // limit the search space for factors (as in C example)
+        long lo = Math.max(tens / 10, (n + tens - 2) / (tens - 1));
+        long hi = Math.min(n / lo, (long) Math.sqrt(n));
+
+        long nTally = tallyDigits(n);
+
+        for (long a = lo; a <= hi; a++) {
+            long b = n / a;
+
+            if (a * b != n)
+                continue;
+
+            // check for mod 9 congruence
+            if (n % 9 != (a + b) % 9)
+                continue;
+
+            if (a % 10 == 0 && b % 10 == 0)
+                continue;
+
+            if (nTally == tallyDigits(a) + tallyDigits(b)) {
+                if (countFangs == 0)
+                    System.out.printf("\n%d : ", n);
+                System.out.printf("[%d, %d]", a, b);
+                countFangs++;
+            }
+        }
+        return countFangs;
+    }
+
+    // sum to a unique number to represent set of digits (as in C example)
+    private static long tallyDigits(long n) {
+        long total = 0;
+        while (n > 0) {
+            total += 1L << ((n % 10) * 6);
+            n /= 10;
+        }
+        return total;
+    }
+}