private static IEnumerable <TResult> DepthFirstFlattenIterator <TNode, TResult>(this IEnumerable <TNode> source,
Func <TNode, IEnumerable <TNode> > childrenSelector, Func <TNode, int, TResult> resultSelector)
{
var list = source.Select(n => new NodeWithLevel <TNode>(n, 0)).ToLinkedList();
while (list.Count > 0)
{
var current = list.First !.Value;
list.RemoveFirst();
yield return(resultSelector(current.Node, current.Level));
var llNode = list.First;
foreach (var child in childrenSelector(current.Node))
{
var newNode = new NodeWithLevel <TNode>(child, current.Level + 1);
if (llNode != null)
{
list.AddBefore(llNode, newNode);
}
else
{
list.AddLast(newNode);
}
}
}
}
private static void Helper(TreeNode root, List <IList <int> > result)
{
if (root == null)
{
result.Add(new List <int>());
return;
}
else
{
var dict = new Dictionary <int, List <int> >();
var queue = new Queue <NodeWithLevel>();
var start = new NodeWithLevel(1, root);
queue.Enqueue(start);
while (queue.Count > 0)
{
var temp = queue.Dequeue();
if (dict.ContainsKey(temp.level))
{
dict[temp.level].Add(temp.node.data);
}
else
{
dict[temp.level] = new List <int>()
{
temp.node.data
};
}
if (temp.node.left != null)
{
queue.Enqueue(new NodeWithLevel(temp.level + 1, temp.node.left));
}
if (temp.node.right != null)
{
queue.Enqueue(new NodeWithLevel(temp.level + 1, temp.node.right));
}
}
var maxLevel = dict.Keys.Max();
for (var lev = maxLevel; lev >= 1; lev--)
{
result.Add(new List <int>());
((List <int>)result[result.Count - 1]).AddRange(dict[lev]);
}
}
}
private static void Helper(TreeNode root, IList <double> result)
{
var dict = new Dictionary <int, List <int> >();
var queue = new Queue <NodeWithLevel>();
var start = new NodeWithLevel(1, root);
queue.Enqueue(start);
while (queue.Count > 0)
{
var temp = queue.Dequeue();
if (dict.ContainsKey(temp.level))
{
dict[temp.level].Add(temp.node.data);
}
else
{
dict[temp.level] = new List <int>()
{
temp.node.data
};
}
if (temp.node.left != null)
{
queue.Enqueue(new NodeWithLevel(temp.level + 1, temp.node.left));
}
if (temp.node.right != null)
{
queue.Enqueue(new NodeWithLevel(temp.level + 1, temp.node.right));
}
}
var maxLevel = dict.Keys.Max();
for (var lev = 1; lev <= maxLevel; lev++)
{
var nodes = dict[lev];
var avg = nodes.Sum() / nodes.Count();
result.Add(avg);
}
}
public IList <IList <int> > LevelOrder(TreeNode root)
{
List <IList <int> > result = new List <IList <int> >();
if (root == null)
{
return(result);
}
Queue <NodeWithLevel> dfsQueue = new Queue <NodeWithLevel>();
dfsQueue.Enqueue(new NodeWithLevel(root, 0));
while (dfsQueue.Count > 0)
{
List <int> currentLevel = new List <int>();
NodeWithLevel currentNode = dfsQueue.Dequeue();
if (currentNode.nodeLevel >= result.Count)
{
currentLevel.Add(currentNode.node.val);
result.Add(currentLevel);
}
else
{
result[currentNode.nodeLevel].Add(currentNode.node.val);
}
if (currentNode.node.left != null)
{
NodeWithLevel newNode = new NodeWithLevel(currentNode.node.left, currentNode.nodeLevel + 1);
dfsQueue.Enqueue(newNode);
}
if (currentNode.node.right != null)
{
NodeWithLevel newNode = new NodeWithLevel(currentNode.node.right, currentNode.nodeLevel + 1);
dfsQueue.Enqueue(newNode);
}
}
return(result);
}
