public void PostorderNoRecursion(BinTreeNode tree, List <long> orderList)
{
Stack <BinTreeNode> stack = new Stack <BinTreeNode>();
HashSet <BinTreeNode> visited = new HashSet <BinTreeNode>();
stack.Push(tree);
while (stack.Count > 0)
{
BinTreeNode crt = stack.Peek();
if (!visited.Contains(crt))
{
visited.Add(crt);
if (null != crt.Right)
{
stack.Push(crt.Right);
}
if (null != crt.Left)
{
stack.Push(crt.Left);
}
}
else
{
orderList.Add(crt.Info);
stack.Pop();
}
}
}
public long[] BreadthFirst(BinTreeNode tree)
{
Queue <BinTreeNode> queue = new Queue <BinTreeNode>();
Queue <long> results = new Queue <long>();
if (null != tree)
{
queue.Enqueue(tree);
while (queue.Count > 0)
{
BinTreeNode node = queue.Dequeue();
if (null != node.Left)
{
queue.Enqueue(node.Left);
}
if (null != node.Right)
{
queue.Enqueue(node.Right);
}
results.Enqueue(node.Info);
}
}
return(results.ToArray());
}
public long[] DepthFirst(BinTreeNode tree)
{
Stack <BinTreeNode> stack = new Stack <BinTreeNode>();
Queue <long> results = new Queue <long>();
if (null != tree)
{
stack.Push(tree);
while (stack.Count > 0)
{
BinTreeNode node = stack.Pop();
if (null != node.Right)
{
stack.Push(node.Right);
}
// push left last to search it first
if (null != node.Left)
{
stack.Push(node.Left);
}
results.Enqueue(node.Info);
}
}
return(results.ToArray());
}
/// <summary>
/// sum all values on each level, for a BST tree
/// </summary>
/// <param name="node"></param>
/// <returns></returns>
public long[] LevelSum(BinTreeNode node)
{
List <long> sums = new List <long>();
int level = 0;
LevelSum(node, level, sums);
return(sums.ToArray());
}
public long [] Inorder(BinTreeNode tree)
{
List <long> results = new List <long>();
if (null != tree)
{
results.AddRange(Inorder(tree.Left));
results.Add(tree.Info);
results.AddRange(Inorder(tree.Right));
}
return(results.ToArray());
}
public bool IsBST(BinTreeNode tree, out long min, out long max)
{
min = max = long.MinValue;
if (null == tree ||
(null != tree.Left && tree.Left.Info > tree.Info) ||
(null != tree.Right && tree.Right.Info < tree.Info)
)
{
return(false);
}
min = max = tree.Info;
if (null != tree.Left)
{
long minLeft, maxLeft;
if (!IsBST(tree.Left, out minLeft, out maxLeft))
{
return(false);
}
if (maxLeft > tree.Info)
{
return(false);
}
min = minLeft;
}
if (null != tree.Right)
{
long minRight, maxRight;
if (!IsBST(tree.Right, out minRight, out maxRight))
{
return(false);
}
if (minRight < tree.Info)
{
return(false);
}
max = maxRight;
}
return(true);
}
private void LevelSum(BinTreeNode node, int level, List <long> sums)
{
if (null == node)
{
return;
}
// add to sums[level]
if (sums.Count <= level)
{
sums.Add(node.Info);
}
else
{
sums[level] += node.Info;
}
LevelSum(node.Left, level + 1, sums);
LevelSum(node.Right, level + 1, sums);
}
public void PreorderNoRecursion(BinTreeNode tree, List <long> orderList)
{
Stack <BinTreeNode> stack = new Stack <BinTreeNode>();
stack.Push(tree);
while (stack.Count > 0)
{
BinTreeNode crt = stack.Pop();
orderList.Add(crt.Info);
if (null != crt.Right)
{
stack.Push(crt.Right);
}
if (null != crt.Left)
{
stack.Push(crt.Left);
}
}
}
public BinTreeNode GetBSTFromPreorder(long[] elements)
{
if (elements.Length == 0)
{
return(null);
}
BinTreeNode root = new BinTreeNode(elements[0]);
//List<long> leftElements = new List<long>();
//List<long> rightElements = new List<long>();
int idx = 1;
int leftMaxIdx = 0, rightMaxIdx = 0;;
while (idx < elements.Length && elements[idx] < root.Info)
{
idx++;
}
leftMaxIdx = idx - 1;
while (idx < elements.Length && elements[idx] > root.Info)
{
idx++;
}
rightMaxIdx = idx - 1;
if (idx != elements.Length)
{
throw new System.InvalidOperationException("no matching BST for the given preorder!");
}
long[] leftElements = elements.Skip(1).Take(leftMaxIdx).ToArray();
long[] rightElements = elements.Skip(1 + leftMaxIdx).Take(rightMaxIdx - leftMaxIdx).ToArray();
root.Left = GetBSTFromPreorder(leftElements);
root.Right = GetBSTFromPreorder(rightElements);
return(root);
}
// min value for null childrens
public BinTreeNode(long info, long left, long right)
{
this.Info = info;
if (long.MinValue != left)
{
this.Left = new BinTreeNode(left);
}
else
{
Left = null;
}
if (long.MinValue != right)
{
this.Right = new BinTreeNode(right);
}
else
{
this.Left = null;
}
}
// building a tree
public BinTreeNode(long info)
{
this.Info = info;
Left = null;
Right = null;
}