Data commit

Task/Hamming-numbers/Groovy/hamming-numbers.groovy

@@ -0,0 +1,38 @@
+class Hamming {
+
+    static final ONE = BigInteger.ONE
+    static final THREE = BigInteger.valueOf(3)
+    static final FIVE = BigInteger.valueOf(5)
+
+    static void main(args) {
+        print 'Hamming(1 .. 20) ='
+        (1..20).each {
+            print " ${hamming it}"
+        }
+        println "\nHamming(1691) = ${hamming 1691}"
+        println "Hamming(1000000) = ${hamming 1000000}"
+    }
+
+    static hamming(n) {
+        def priorityQueue = new PriorityQueue<BigInteger>()
+        priorityQueue.add ONE
+
+        def lowest
+
+        n.times {
+            lowest = priorityQueue.poll()
+            while (priorityQueue.peek() == lowest) {
+                priorityQueue.poll()
+            }
+            updateQueue(priorityQueue, lowest)
+        }
+
+        lowest
+    }
+
+    static updateQueue(priorityQueue, lowest) {
+        priorityQueue.add(lowest.shiftLeft 1)
+        priorityQueue.add(lowest.multiply THREE)
+        priorityQueue.add(lowest.multiply FIVE)
+    }
+}