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copied!<p>Here is a combination iterator I wrote recetnly</p> <pre><code>package psychicpoker; import java.util.ArrayList; import java.util.Collection; import java.util.Iterator; import java.util.List; import static com.google.common.base.Preconditions.checkArgument; public class CombinationIterator<T> implements Iterator<Collection<T>> { private int[] indices; private List<T> elements; private boolean hasNext = true; public CombinationIterator(List<T> elements, int k) throws IllegalArgumentException { checkArgument(k<=elements.size(), "Impossible to select %d elements from hand of size %d", k, elements.size()); this.indices = new int[k]; for(int i=0; i<k; i++) indices[i] = k-1-i; this.elements = elements; } public boolean hasNext() { return hasNext; } private int inc(int[] indices, int maxIndex, int depth) throws IllegalStateException { if(depth == indices.length) { throw new IllegalStateException("The End"); } if(indices[depth] < maxIndex) { indices[depth] = indices[depth]+1; } else { indices[depth] = inc(indices, maxIndex-1, depth+1)+1; } return indices[depth]; } private boolean inc() { try { inc(indices, elements.size() - 1, 0); return true; } catch (IllegalStateException e) { return false; } } public Collection<T> next() { Collection<T> result = new ArrayList<T>(indices.length); for(int i=indices.length-1; i>=0; i--) { result.add(elements.get(indices[i])); } hasNext = inc(); return result; } public void remove() { throw new UnsupportedOperationException(); } </code></pre> <p>}</p>

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