Initial data commit

Task/Prime-decomposition/Java/prime-decomposition-4.java

@@ -0,0 +1,43 @@
+private static final BigInteger TWO = BigInteger.valueOf(2);
+private static final BigInteger THREE = BigInteger.valueOf(3);
+private static final BigInteger FIVE = BigInteger.valueOf(5);
+
+public static ArrayList<BigInteger> primeDecomp(BigInteger n){
+    if(n.compareTo(TWO) < 0) return null;
+    ArrayList<BigInteger> factors = new ArrayList<BigInteger>();
+
+    // handle even values
+    while(n.and(BigInteger.ONE).equals(BigInteger.ZERO)){
+        n = n.shiftRight(1);
+        factors.add(TWO);
+    }
+
+    // handle values divisible by three
+    while(n.mod(THREE).equals(BigInteger.ZERO)){
+        factors.add(THREE);
+        n = n.divide(THREE);
+    }
+
+    // handle values divisible by five
+    while(n.mod(FIVE).equals(BigInteger.ZERO)){
+        factors.add(FIVE);
+        n = n.divide(FIVE);
+    }
+
+    // much like how we can skip multiples of two, we can also skip
+    // multiples of three and multiples of five. This increment array
+    // helps us to accomplish that
+    int[] pattern = {4,2,4,2,4,6,2,6};
+    int pattern_index = 0;
+    BigInteger current_test = BigInteger.valueOf(7);
+    while(!n.equals(BigInteger.ONE)){
+        while(n.mod(current_test).equals(BigInteger.ZERO)){
+            factors.add(current_test);
+            n = n.divide(current_test);
+        }
+        current_test = current_test.add(BigInteger.valueOf(pattern[pattern_index]));
+        pattern_index = (pattern_index + 1) & 7;
+    }
+
+    return factors;
+}