private static IEnumerable <Tuple <IMultiwayTreeNode, TLevel> > LevelOrderTraverse <TLevel>(
IMultiwayTreeNode partialroot,
TLevel seed,
Func <TLevel, IMultiwayTreeNode, int, TLevel> levelfunc)
{
var queue = new Queue <Tuple <IMultiwayTreeNode, TLevel> >();
queue.Enqueue(new Tuple <IMultiwayTreeNode, TLevel>(partialroot, seed));
int index;
while (queue.Count > 0)
{
index = 0;
var current = queue.Dequeue();
if (SentinelEx.NotEqualNull(current.Item1.Children))
{
foreach (var node in current.Item1.Children)
{
queue.Enqueue(new Tuple <IMultiwayTreeNode, TLevel>(node,
levelfunc == null ? current.Item2 : levelfunc(current.Item2, partialroot, index++)));
}
}
yield return(current);
}
}
public static IEnumerable <IMultiwayTreeNode> TraverseSubtree(this IMultiwayTreeNode partialroot, TraverseOrder order = TraverseOrder.LevelOrder)
{
Contract.Requires <ArgumentNullException>(partialroot != null);
Contract.Requires <NotSupportedException>(order != TraverseOrder.InOrder, "多叉树不支持中序遍历");
Contract.Ensures(Contract.Result <IEnumerable <IMultiwayTreeNode> >() != null);
return(partialroot.TraverseSubtree <object>(null, null, order).Select(res => res.Item1));
}
private static bool AreChildrenLeftPadding(this IMultiwayTreeNode node)
{
if (node.Children == null)
{
return(true);
}
bool flag = true;
foreach (var t in node.Children)
{
if (t != null && !flag)
{
return(false);
}
else
{
flag = false;
}
}
return(true);
}
/// <summary>
/// enumerate the subtree with the root <paramref name="partialroot"/>, provided with certain information (of type <typeparamref name="TLevel"/>) of the node
/// 遍历以<paramref name="partialroot"/>为根的子树，并且在过程中提供结点有关信息(<typeparamref name="TLevel"/>类型的)
/// </summary>
/// <typeparam name="TLevel">提供的每层结点额外信息的类型</typeparam>
/// <param name="partialroot">需要遍历的子树的根</param>
/// <param name="seed">附加参数的初始值</param>
/// <param name="levelfunc">遍历到某一层结点时将附加参数传给下一层孩子时需要进行的操作。第一个参数是该层的附加参数，
/// 第二个参数是遍历到的结点，第三个是遍历到的结点在上层结点孩子结点中的编号</param>
/// <param name="order">多叉树遍历方式</param>
/// <returns>遍历得到的结点与附加参数的集合</returns>
public static IEnumerable <Tuple <IMultiwayTreeNode, TLevel> > TraverseSubtree <TLevel>(
this IMultiwayTreeNode partialroot,
TLevel seed,
Func <TLevel, IMultiwayTreeNode, int, TLevel> levelfunc,
TraverseOrder order = TraverseOrder.LevelOrder)
{
Contract.Requires <ArgumentNullException>(partialroot != null);
Contract.Requires <NotSupportedException>(order != TraverseOrder.InOrder, "多叉树不支持中序遍历");
Contract.Ensures(Contract.Result <IEnumerable <Tuple <IMultiwayTreeNode, TLevel> > >() != null);
var current = new Tuple <IMultiwayTreeNode, TLevel>[] { new Tuple <IMultiwayTreeNode, TLevel>(partialroot, seed) };
switch (order)
{
case TraverseOrder.PreOrder:
return(current.Concat(partialroot.Children?
.SelectMany((node, index) => node?.TraverseSubtree(
levelfunc == null ? seed : levelfunc(seed, partialroot, index), levelfunc, order)
?? Enumerable.Empty <Tuple <IMultiwayTreeNode, TLevel> >())
?? Enumerable.Empty <Tuple <IMultiwayTreeNode, TLevel> >()));
case TraverseOrder.PostOrder:
return((partialroot.Children?
.SelectMany((node, index) => node?.TraverseSubtree(
levelfunc == null ? seed : levelfunc(seed, partialroot, index), levelfunc, order)
?? Enumerable.Empty <Tuple <IMultiwayTreeNode, TLevel> >())
?? Enumerable.Empty <Tuple <IMultiwayTreeNode, TLevel> >())
.Reverse().Concat(current));
case TraverseOrder.LevelOrder:
return(LevelOrderTraverse(partialroot, seed, levelfunc));
default:
return(null);
}
}
public static int GetDegree(this IMultiwayTreeNode node)
{
Contract.Requires <ArgumentNullException>(node == null);
Contract.Ensures(Contract.Result <int>() >= 0);
return(node.Children?.Count(cnode => SentinelEx.NotEqualNull(cnode)) ?? 0);
}
