hello-algo/codes/csharp/include/TreeNode.cs

/**
 * File: TreeNode.cs
 * Created Time: 2022-12-23
 * Author: haptear (haptear@hotmail.com)
 */

namespace hello_algo.include
{
    public class TreeNode
    {
        public int val;        // 结点值
        public int height;     // 结点高度
        public TreeNode? left;  // 左子结点引用
        public TreeNode? right; // 右子结点引用

        public TreeNode(int x)
        {
            val = x;
        }

        /**
         * Generate a binary tree given an array
         * @param arr
         * @return
         */
        public static TreeNode? ArrToTree(int?[] arr)
        {
            if (arr.Length == 0 || arr[0] == null)
                return null;

            TreeNode root = new TreeNode((int) arr[0]);
            Queue<TreeNode> queue = new Queue<TreeNode>();
            queue.Enqueue(root);
            int i = 0;
            while (queue.Count != 0)
            {
                TreeNode node = queue.Dequeue();
                if (++i >= arr.Length) break;
                if (arr[i] != null)
                {
                    node.left = new TreeNode((int) arr[i]);
                    queue.Enqueue(node.left);
                }
                if (++i >= arr.Length) break;
                if (arr[i] != null)
                {
                    node.right = new TreeNode((int) arr[i]);
                    queue.Enqueue(node.right);
                }
            }
            return root;
        }

        /**
         * Serialize a binary tree to a list
         * @param root
         * @return
         */
        public static List<int?> TreeToList(TreeNode root)
        {
            List<int?> list = new();
            if (root == null) return list;
            Queue<TreeNode?> queue = new();
            while (queue.Count != 0)
            {
                TreeNode? node = queue.Dequeue();
                if (node != null)
                {
                    list.Add(node.val);
                    queue.Enqueue(node.left);
                    queue.Enqueue(node.right);
                }
                else
                {
                    list.Add(null);
                }
            }
            return list;
        }

        /**
         * Get a tree node with specific value in a binary tree
         * @param root
         * @param val
         * @return
         */
        public static TreeNode? GetTreeNode(TreeNode? root, int val)
        {
            if (root == null)
                return null;
            if (root.val == val)
                return root;
            TreeNode? left = GetTreeNode(root.left, val);
            TreeNode? right = GetTreeNode(root.right, val);
            return left != null ? left : right;
        }
    }
}