哈弗曼算法_C#代码
这是链接上一篇文章所写的代码，上一篇链接如下：
http://www.cnblogs.com/HONT/archive/2013/06/05/3118531.html
StringToHuffmanCode这个函数相当于把转换步奏打包执行，其中树的一些遍历使用递归实现，由于用了不少.Net3.5的特性，造成看着费劲实在抱歉。。
public string StringToHuffmanCode(out Dictionary<char, string> key, string str) { string result = ""; var tmps = GetWeightArray(str); //构建权值数组 var tree = CreateHuffmanTree(tmps); //构建哈弗曼树,即最优二叉树 var dict = CreateHuffmanDict(tree); //构建哈弗曼字典. result = ToHuffmanCode(str, dict); //输出哈弗曼代码 key = dict; return result; }
下面给出全部代码
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在VS2012和.Net3.5中 测试通过.
具体实现:按照权值提取数据 - 转换最优二叉树 - 进行编码 - 返回字典和编码后文件
首先是Main函数中的代码:
class Program { static void Main(string[] args) { string source = "哈夫曼曼曼曼曼"; Huffman hf = new Huffman(); Dictionary<char, string> key = null; var hfCode = hf.StringToHuffmanCode(out key, source); Console.WriteLine("--------------------编码与解析"); Console.WriteLine("编码: "+hfCode); var text = hf.ToText(hfCode, key); Console.WriteLine("解析: " + text); Console.ReadLine(); } }
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然后是类里面的代码:
using System; using System.Collections.Generic; using System.Linq; public class Huffman { public class Node : IComparable { /// <summary> /// 左子树 /// </summary> public Node LChild { get; set; } /// <summary> /// 右子树 /// </summary> public Node RChild { get; set; } /// <summary> /// 权值 /// </summary> public int Weight { get; set; } /// <summary> /// 原字符 /// </summary> public char Key { get; set; } public Node() { } public Node(int weight, char value) { this.Weight = weight; this.Key = value; } /// <summary> /// 实现比较接口，用于排序 /// </summary> public int CompareTo(object obj) { int result = 0; Node tmp = obj as Node; if (tmp.Weight > this.Weight) { result = 1; } else if (tmp.Weight < this.Weight) { result = -1; } return result; } } /// <summary> /// 获得权值数组 /// </summary> /// <param name="str"></param> /// <returns></returns> public Node[] GetWeightArray(string str) { List<Node> result = new List<Node>(); char[] charArr = str.ToCharArray(); while (charArr.Length > 0) { char[] cntChars = null; var tmp = charArr.Where(m => m == charArr[0]); cntChars = new char[tmp.Count()]; tmp.ToArray().CopyTo(cntChars, 0); charArr = charArr.Where(m => m != tmp.First()).ToArray(); result.Add(new Node(cntChars.Length, cntChars[0])); } return result.ToArray(); } /// <summary> /// 构建哈弗曼树 /// </summary> /// <param name="sources">权值数组</param> /// <returns>返回哈弗曼树根</returns> public Node CreateHuffmanTree(Node[] sources) { Node result = null; Node[] nodes = sources; bool isNext = true; while (isNext) { if (nodes.Length == 2) { result = new Node(); result.LChild = nodes[0]; result.RChild = nodes[1]; isNext = false; } Array.Sort(nodes); Node n1 = nodes[nodes.Length - 1]; Node n2 = nodes[nodes.Length - 2]; Node tmp = new Node(); tmp.Weight = n1.Weight + n2.Weight; tmp.LChild = n1; tmp.RChild = n2; Node[] tmpNds = new Node[nodes.Length - 1]; Array.Copy(nodes, 0, tmpNds, 0, nodes.Length - 1); tmpNds[tmpNds.Length - 1] = tmp; nodes = tmpNds; } return result; } /// <summary> /// 字符串转换为哈弗曼代码.当然可以改成二进制数据 /// </summary> /// <param name="key">编码字典</param> /// <param name="str">传入字符串</param> /// <returns>编码后的字符串</returns> public string StringToHuffmanCode(out Dictionary<char, string> key, string str) { string result = ""; var tmps = GetWeightArray(str); var tree = CreateHuffmanTree(tmps); var dict = CreateHuffmanDict(tree); foreach (var item in dict) { Console.WriteLine(item); } result = ToHuffmanCode(str, dict); key = dict; return result; } /// <summary> /// 创建哈弗曼代码字典 /// </summary> /// <param name="hTree">哈弗曼树</param> /// <returns></returns> public Dictionary<char, string> CreateHuffmanDict(Node hTree) { return CreateHuffmanDict("", hTree); } private Dictionary<char, string> CreateHuffmanDict(string code, Node hTree) { Dictionary<char, string> result = new Dictionary<char, string>(); if (hTree.LChild == null && hTree.RChild == null) { result.Add(hTree.Key, code); } else { var dictL = CreateHuffmanDict(code + "0", hTree.LChild); var dictR = CreateHuffmanDict(code + "1", hTree.RChild); foreach (var item in dictL) { result.Add(item.Key, item.Value); } foreach (var item in dictR) { result.Add(item.Key, item.Value); } } return result; } /// <summary> /// 源字符串转换到哈弗曼代码 /// </summary> /// <param name="source">源字符串</param> /// <param name="hfdict">哈弗曼代码字典</param> /// <returns>编译后代码</returns> public string ToHuffmanCode(string source, Dictionary<char, string> hfdict) { string result = ""; for (int i = 0; i < source.Length; i++) { result += hfdict.First(m => m.Key == source[i]).Value; } return result; } /// <summary> /// 解析回字符串 /// </summary> /// <param name="code">哈弗曼代码</param> /// <param name="hfdict">哈弗曼代码字典</param> /// <returns>解析后字符串</returns> public string ToText(string code, Dictionary<char, string> hfdict) { string result = ""; for (int i = 0; i < code.Length; ) { foreach (var item in hfdict) { if ( code[i] == item.Value[0] && item.Value.Length + i <= code.Length) { char[] tmpArr = new char[item.Value.Length]; Array.Copy(code.ToCharArray(), i, tmpArr, 0, tmpArr.Length); if (new String(tmpArr) == item.Value) { result += item.Key; i += item.Value.Length; break; } } } } return result; } }