tree_contester_1

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.IO;
// sollution 1
namespace ConsoleApplication
{
    class BinaryTree
    {
        private class Node
        {
            public char inf;
            public Node left;
            public Node right;

            public Node(char inf_)
            {
                inf = inf_;
                left = null;
                right = null;
            }

            public static void FormTree(ref Node r, char tmp)
            {
                if (r == null)
                    r = new Node(tmp);
                else if (r.left == null)
                   FormTree(ref r.left, tmp);
                else FormTree(ref r.right, tmp);
            }

            public static void Preorder(Node r, StreamWriter fin)
            {
                if (r != null)
                {
                    Preorder(r.left, fin);
                    fin.Write("{0}", r.inf);
                    Preorder(r.right, fin);
                }
            }
        }
        Node tree;

        public BinaryTree()
        {
            tree = null;
        }

        private BinaryTree(Node r)
        {
            tree = r;
        }

        public void FormTree(string nameOfFile)
        {
            StreamReader fin = new StreamReader(nameOfFile);
            string tmp = fin.ReadLine();
            fin.Close();
            Queue<char> letters = new Queue<char>();
            Queue<char> symbols = new Queue<char>();
            for (int i = 0; i < tmp.Length; i++)
            {
                if (tmp[i] == '/' || '+' == tmp[i] || tmp[i] == '*' || tmp[i] == '-')
                    symbols.Enqueue(tmp[i]);
                else letters.Enqueue(tmp[i]);
            }
            foreach (char i in symbols)
            {
                Node.FormTree(ref tree, i);
                Node.FormTree(ref tree, letters.Peek());
                letters.Dequeue();
            }
            Node.FormTree(ref tree, letters.Peek());
        }

        public void Preorder(string nameOfFile)
        {
            StreamWriter fin = new StreamWriter(nameOfFile);
            Node.Preorder(tree, fin);
            fin.Close();
        }

    }
    class Program
    {

        static void Main(string[] args)
        {
            BinaryTree t = new BinaryTree();
            t.FormTree("input.txt");
            t.Preorder("output.txt");
        }

    }
}

// solution 2

    class BinaryTree
    {
        private class Node
        {
            public char inf;
            public Node left;
            public Node right;

            public Node(char inf_)
            {
                inf = inf_;
                left = null;
                right = null;
            }

            public static void FormTree(ref Node r, char tmp, ref bool flag)
            {
                if (r == null)
                {
                    r = new Node(tmp);
                    flag = true;
                }
                else
                {
                    if (!(r.inf == '/' || '+' == r.inf || r.inf == '*' || r.inf == '-'))
                        return;

                    FormTree(ref r.left, tmp, ref flag);

                    if (!flag) FormTree(ref r.right, tmp, ref flag);
                }
            }

            public static void Preorder(Node r, StreamWriter fin)
            {
                if (r != null)
                {
                    Preorder(r.left, fin);
                    fin.Write("{0}", r.inf);
                    Preorder(r.right, fin);
                }
            }

        }
        Node tree;

        public BinaryTree()
        {
            tree = null;
        }

        private BinaryTree(Node r)
        {
            tree = r;
        }

        public void FormTree(string nameOfFile)
        {
            StreamReader fin = new StreamReader(nameOfFile);
            string tmp = fin.ReadLine();
            fin.Close();
            bool flag = false;
            foreach (char i in tmp)
            {
                flag = false;
                Node.FormTree(ref tree, i, ref flag);
            }
        }

        public void Preorder(string nameOfFile)
        {
            StreamWriter fin = new StreamWriter(nameOfFile);
            Node.Preorder(tree, fin);
            fin.Close();
        }

    }
    class Program
    {
        static void Main(string[] args)
        {
            BinaryTree t = new BinaryTree();
            t.FormTree("input.txt");
            t.Preorder("output.txt");
        }
    }