Efficient iteration over all possible combinations of variable assignments, for variables of arbitrary cardinalities

git-svn-id: file:///humgen/gsa-scr1/gsa-engineering/svn_contents/trunk@4059 348d0f76-0448-11de-a6fe-93d51630548a

java/src/org/broadinstitute/sting/utils/CardinalityCounter.java

@@ -0,0 +1,67 @@
+package org.broadinstitute.sting.utils;
+
+import java.util.Iterator;
+
+/**
+ * Created by IntelliJ IDEA.
+ * User: fromer
+ * Date: Aug 19, 2010
+ * Time: 9:33:54 AM
+ * To change this template use File | Settings | File Templates.
+ */
+
+/*
+* CardinalityCounter object allows user to iterate over all assignment of arbitrary-cardinality variables.
+ */
+public class CardinalityCounter implements Iterator<int[]>, Iterable<int[]> {
+    private int[] cards;
+    private int[] valList;
+    private boolean hasNext;
+
+    public CardinalityCounter(int[] cards) {
+        this.cards = cards;
+        this.valList = new int[cards.length];
+        for (int i = 0; i < cards.length; i++) {
+            if (this.cards[i] <= 0)
+                throw new IllegalArgumentException("CANNOT have zero cardinalities!");
+            this.valList[i] = 0;
+        }
+        this.hasNext = true;
+    }
+
+    public boolean hasNext() {
+        return hasNext;
+    }
+
+    public int[] next() {
+        if (!hasNext())
+            throw new StingException("CANNOT iterate past end!");
+
+        // Copy the assignment to be returned:
+        int[] nextList = new int[valList.length];
+        for (int i = 0; i < valList.length; i++)
+            nextList[i] = valList[i];
+
+        // Find the assignment after this one:
+        hasNext = false;
+        int i = cards.length - 1;
+        for (; i >= 0; i--) {
+            if (valList[i] < (cards[i] - 1)) {
+                valList[i]++;
+                hasNext = true;
+                break;
+            }
+            valList[i] = 0;
+        }
+
+        return nextList;
+    }
+
+    public void remove() {
+        throw new RuntimeException("Cannot remove from CardinalityCounter!");
+    }
+
+    public Iterator<int[]> iterator() {
+        return this;
+    }
+}