public static void FindSum(TreeNode node, int sum, int[] path, int level)
{
if (node == null)
{
return;
}
/* Insert current node into path */
path[level] = node.Data;
var t = 0;
for (var i = level; i >= 0; i--)
{
t += path[i];
if (t == sum)
{
Print(path, i, level);
}
}
FindSum(node.Left, sum, path, level + 1);
FindSum(node.Right, sum, path, level + 1);
/* Remove current node from path. Not strictly necessary, since we would
* ignore this value, but it's good practice.
*/
path[level] = Int32.MinValue;
}
public void SetLeftChild(TreeNode left)
{
this.Left = left;
if (left != null) {
left.Parent = this;
}
}
public void SetRightChild(TreeNode right)
{
this.Right = right;
if (right != null) {
right.Parent = this;
}
}
public static TreeNode InorderSucc(TreeNode node)
{
if (node == null)
{
return null;
}
// Found right children -> return left most node of right subtree
if (node.Parent == null || node.Right != null)
{
return LeftMostChild(node.Right);
}
var q = node;
var x = q.Parent;
// Go up until we’re on left instead of right
while (x != null && x.Left != q)
{
q = x;
x = x.Parent;
}
return x;
}
int CheckHeight(TreeNode root)
{
if (root == null)
{
return 0;
}
int leftHeight = CheckHeight(root.Left);
if (leftHeight == -1)
{
return -1;
}
int rightHeight = CheckHeight(root.Right);
if (rightHeight == -1)
{
return -1;
}
int heightDiff = leftHeight - rightHeight;
if (Math.Abs(heightDiff) > 1)
{
return -1;
}
else
{
return Math.Max(leftHeight, rightHeight) + 1;
}
}
public static void FindSum(TreeNode node, int sum)
{
var depth = Depth(node);
var path = new int[depth];
FindSum(node, sum, path, 0);
}
int GetHeight(TreeNode root)
{
if (root == null)
{
return 0;
}
return Math.Max(GetHeight(root.Left), GetHeight(root.Right)) + 1;
}
public static bool ContainsTree(TreeNode t1, TreeNode t2)
{
if (t2 == null)
{
return true; // The empty tree is a subtree of every tree.
}
return SubTree(t1, t2);
}
public static int Depth(TreeNode node)
{
if (node == null)
{
return 0;
}
return 1 + Math.Max(Depth(node.Left), Depth(node.Right));
}
bool IsBalancedImproved(TreeNode root)
{
if (CheckHeight(root) == -1)
{
return false;
}
else
{
return true;
}
}
public void Run()
{
var root = new TreeNode(5);
root.Left = new TreeNode(3);
root.Right = new TreeNode(1);
root.Left.Left = new TreeNode(4);
root.Left.Right = new TreeNode(8);
root.Right.Left = new TreeNode(2);
root.Right.Right = new TreeNode(6);
FindSum(root, 8);
}
public static TreeNode LeftMostChild(TreeNode node)
{
if (node == null)
{
return null;
}
while (node.Left != null)
{
node = node.Left;
}
return node;
}
bool IsBalanced(TreeNode root)
{
if (root == null)
{
return true;
}
int heightDiff = GetHeight(root.Left) - GetHeight(root.Right);
if (Math.Abs(heightDiff) > 1)
{
return false;
}
else
{
return IsBalanced(root.Left) && IsBalanced(root.Right);
}
}
/* Checks if the binary tree rooted at node1 contains the binary tree
* rooted at node2 as a subtree somewhere within it.
*/
public static bool SubTree(TreeNode node1, TreeNode node2)
{
if (node1 == null)
{
// big tree empty & subtree still not found.
return false;
}
if (node1.Data == node2.Data)
{
if (MatchTree(node1, node2))
{
return true;
}
}
return (SubTree(node1.Left, node2) || SubTree(node1.Right, node2));
}
/* Creates tree by mapping the array left to right, top to bottom. */
public static TreeNode CreateTreeFromArray(int[] array)
{
if (array.Length > 0)
{
var root = new TreeNode(array[0]);
var queue = new Queue<TreeNode>();
queue.Enqueue(root);
var done = false;
var i = 1;
while (!done)
{
var treeNode = queue.Peek();
if (treeNode.Left == null)
{
treeNode.Left = new TreeNode(array[i]);
i++;
queue.Enqueue(treeNode.Left);
}
else if (treeNode.Right == null)
{
treeNode.Right = new TreeNode(array[i]);
i++;
queue.Enqueue(treeNode.Right);
}
else
{
queue.Dequeue();
}
if (i == array.Length)
{
done = true;
}
}
return root;
}
return null;
}
public void Run()
{
// Create balanced tree
int[] array = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
var root = TreeNode.CreateMinimalBst(array);
Console.WriteLine("Root? " + root.Data);
Console.WriteLine("Is balanced? " + IsBalanced(root));
Console.WriteLine("Improved Is balanced? " + IsBalancedImproved(root));
// Could be balanced, actually, but it's very unlikely...
var unbalanced = new TreeNode(10);
for (var i = 0; i < 10; i++)
{
unbalanced.InsertInOrder(AssortedMethods.RandomIntInRange(0, 100));
}
Console.WriteLine("Root? " + unbalanced.Data);
Console.WriteLine("Is balanced? " + IsBalanced(unbalanced));
Console.WriteLine("Improved Is balanced? " + IsBalancedImproved(unbalanced));
}
/* Checks if the binary tree rooted at node1 contains the
* binary tree rooted at node2 as a subtree starting at node1.
*/
public static bool MatchTree(TreeNode node1, TreeNode node2)
{
if (node2 == null && node1 == null)
{
// nothing left in the subtree
return true;
}
if (node1 == null || node2 == null)
{
// big tree empty & subtree still not found
return false;
}
if (node1.Data != node2.Data)
{
// data doesn’t match
return false;
}
return (MatchTree(node1.Left, node2.Left) && MatchTree(node1.Right, node2.Right));
}
// Checks how many “special” nodes are located under this root
public static int Covers(TreeNode root, TreeNode p, TreeNode q)
{
var nodesFound = NoNodesFound;
if (root == null)
{
return nodesFound;
}
if (root == p || root == q)
{
nodesFound += 1;
}
nodesFound += Covers(root.Left, p, q);
if (nodesFound == TwoNodesFound) // Found p and q
{
return nodesFound;
}
return nodesFound + Covers(root.Right, p, q);
}
public static List<LinkedList<TreeNode>> CreateLevelLinkedList(TreeNode root)
{
var result = new List<LinkedList<TreeNode>>();
/* "Visit" the root */
var current = new LinkedList<TreeNode>();
if (root != null)
{
current.AddFirst(root);
}
while (current.Count > 0)
{
// Add previous level
result.Add(current);
// Go to next level
var parents = current;
current = new LinkedList<TreeNode>();
foreach (var parent in parents)
{
/* Visit the children */
if (parent.Left != null)
{
current.AddLast(parent.Left);
}
if (parent.Right != null)
{
current.AddLast(parent.Right);
}
}
}
return result;
}
private static TreeNode CreateMinimalBst(int[] arr, int start, int end)
{
if (end < start) {
return null;
}
int mid = (start + end) / 2;
TreeNode n = new TreeNode(arr[mid]);
n.SetLeftChild(CreateMinimalBst(arr, start, mid - 1));
n.SetRightChild(CreateMinimalBst(arr, mid + 1, end));
return n;
}
/* Creates tree by mapping the array left to right, top to bottom. */
public static TreeNode CreateTreeFromArray(int[] array) {
if (array.Length > 0) {
TreeNode root = new TreeNode(array[0]);
Queue<TreeNode> queue =
new Queue<TreeNode>();
queue.Enqueue(root);
bool done = false;
int i = 1 ;
while (!done) {
TreeNode r = (TreeNode) queue.Peek();
if (r.Left == null) {
r.Left = new TreeNode(array[i]);
i++;
queue.Enqueue(r.Left);
} else if (r.Right == null) {
r.Right = new TreeNode(array[i]);
i++;
queue.Enqueue(r.Right);
} else {
queue.Dequeue();
}
if (i == array.Length) done = true;
}
return root;
} else {
return null;
}
}
public static TreeNode RandomBst(int N, int min, int max)
{
int d = RandomIntInRange(min, max);
TreeNode root = new TreeNode(d);
for (int i = 1; i < N; i++) {
root.InsertInOrder(RandomIntInRange(min, max));
}
return root;
}
public static TreeNode CommonAncestor(TreeNode root, TreeNode p, TreeNode q)
{
if (q == p && (root.Left == q || root.Right == q))
{
return root;
}
// Check left side
var nodesFromLeft = Covers(root.Left, p, q);
if (nodesFromLeft == TwoNodesFound)
{
if (root.Left == p || root.Left == q)
{
return root.Left;
}
return CommonAncestor(root.Left, p, q);
}
else if (nodesFromLeft == OneNodeFound)
{
if (root == p)
{
return p;
}
else if (root == q)
{
return q;
}
}
// Check right side
var nodesFromRight = Covers(root.Right, p, q);
if (nodesFromRight == TwoNodesFound)
{
if (root.Right == p || root.Right == q)
{
return root.Right;
}
return CommonAncestor(root.Right, p, q);
}
else if (nodesFromRight == OneNodeFound)
{
if (root == p)
{
return p;
}
else if (root == q)
{
return q;
}
}
if (nodesFromLeft == OneNodeFound && nodesFromRight == OneNodeFound)
{
return root;
}
return null;
}
private static TreeNode CreateMinimalBst(int[] array, int start, int end)
{
if (end < start)
{
return null;
}
var mid = (start + end) / 2;
var treeNode = new TreeNode(array[mid]);
treeNode.SetLeftChild(CreateMinimalBst(array, start, mid - 1));
treeNode.SetRightChild(CreateMinimalBst(array, mid + 1, end));
return treeNode;
}