* defined as the <i>least</i> element in the queue according to the queue's comparator. But unlike
 * a regular priority queue, the methods {@link #peekLast}, {@link #pollLast} and {@link
 * #removeLast} are also provided, to act on the <i>greatest</i> element in the queue instead.
 *
 * <p>A min-max priority queue can be configured with a maximum size. If so, each time the size of

 * defined as the <i>least</i> element in the queue according to the queue's comparator. But unlike
 * a regular priority queue, the methods {@link #peekLast}, {@link #pollLast} and {@link
 * #removeLast} are also provided, to act on the <i>greatest</i> element in the queue instead.
 *
 * <p>A min-max priority queue can be configured with a maximum size. If so, each time the size of

    assertEquals(4, (int) mmHeap.pollLast());
    assertEquals(3, (int) mmHeap.peekLast());
    assertEquals(3, (int) mmHeap.pollLast());
    assertEquals(1, (int) mmHeap.peek());
    assertEquals(2, (int) mmHeap.peekLast());
    assertEquals(2, (int) mmHeap.pollLast());
    assertEquals(1, (int) mmHeap.peek());
    assertEquals(1, (int) mmHeap.peekLast());
    assertEquals(1, (int) mmHeap.pollLast());

    assertEquals(4, (int) mmHeap.pollLast());
    assertEquals(3, (int) mmHeap.peekLast());
    assertEquals(3, (int) mmHeap.pollLast());
    assertEquals(1, (int) mmHeap.peek());
    assertEquals(2, (int) mmHeap.peekLast());
    assertEquals(2, (int) mmHeap.pollLast());
    assertEquals(1, (int) mmHeap.peek());
    assertEquals(1, (int) mmHeap.peekLast());
    assertEquals(1, (int) mmHeap.pollLast());

    while (!stack.isEmpty()) {
      // To peek at the top two items, we need to temporarily remove one.
      NodeAndRemainingSuccessors<N> top = stack.removeLast();
      NodeAndRemainingSuccessors<N> prev = stack.peekLast();
      stack.addLast(top);

      N node = top.node;
      N previousNode = prev == null ? null : prev.node;
      if (top.remainingSuccessors == null) {
        NodeVisitState state = visitedNodes.get(node);