huffman编码 c#实现

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Collections.Specialized;
namespace HuffmanCode
{
    public partial class Form1 : Form
    {
        class Node                                 //霍夫曼樹節點結構
        {
            public char code;
            public uint prioirry;                           //保存權值
            public Node lchild;                           //左孩子指針
            public Node rchild;                           //右孩子指針
        }
        public Form1()
        {
            InitializeComponent();

        }

        private Dictionary<char, string> dictcode = new Dictionary<char, string>();
        private Node huffTree;

        private int comparisonNode(Node n1, Node n2)
        {
            return (int)(n1.prioirry - n2.prioirry);
        }

        private string encode(string str)
        {
            dictcode.Clear();
            huffTree = null;
            if (string.IsNullOrEmpty(str))
            {
                return "";
            }
            Dictionary<char, uint> priorityQueue = new Dictionary<char, uint>();

            for (int i = 0; i < str.Length; i++)
            {
                if (priorityQueue.ContainsKey(str[i]))
                {
                    priorityQueue[str[i]]++;
                }
                else
                {
                    priorityQueue.Add(str[i], 1);
                }
            }
            List<Node> listpc = new List<Node>();
            foreach (var item in priorityQueue)
            {
                listpc.Add(new Node() { prioirry = item.Value, lchild = null, rchild = null, code = item.Key });
            }

            listpc.Sort(comparisonNode);

            while (listpc.Count > 1)
            {
                Node n = new Node();
                n.prioirry = listpc[0].prioirry + listpc[1].prioirry;
                n.lchild = listpc[0];
                n.rchild = listpc[1];
                listpc.RemoveAt(0);
                listpc.RemoveAt(0);
                int index = -1;
                for (int i = 0; i < listpc.Count; i++)
                {
                    if (n.prioirry <= listpc[i].prioirry)
                    {
                        index = i;
                        break;
                    }
                }
                if (index == -1) { index = listpc.Count; }
                listpc.Insert(index, n);
            }
            string encodestr = "";
            viewTree(listpc[0], "");
            huffTree = listpc[0];
            for (int i = 0; i < str.Length; i++)
            {
                encodestr += dictcode[str[i]];
            }
            return encodestr;
        }


        private void viewTree(Node n, string v)
        {
            if (n.code != '\0')
            {
                dictcode.Add(n.code, v);
            }
            else
            {
                if (n.lchild != null)
                {
                    string vl = v + "0";
                    viewTree(n.lchild, vl);
                }
                if (n.rchild != null)
                {
                    string vr = v + "1";
                    viewTree(n.rchild, vr);
                }
            }
        }

        private string decode(string str)
        {
            Node root = huffTree;
            string result = "";
            for (int i = 0; i < str.Length; i++)
            {
                if (root.code != '\0')
                {
                    result += root.code.ToString();
                    root = huffTree;
                }

                if (str[i] == '0')
                {
                    root = root.lchild;
                }
                else
                {
                    root = root.rchild;
                }
            }
            if (root.code != '\0')
            {
                result += root.code.ToString();
            }
            return result;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            textBox2.Text = encode(textBox1.Text);
        }

        private void button2_Click(object sender, EventArgs e)
        {
            textBox3.Text = decode(textBox2.Text);
        }
    }
}