哈夫曼编码解码 C++实现

哈夫曼编码是一个通过哈夫曼树进行的一种编码，一般情况下，以字符：‘0’与‘1’表示。编码的实现过程很简单，只要实现哈夫曼树，通过遍历哈夫曼树，这里我们从每一个叶子结点开始向上遍历，如果该结点为父节点的左孩子，则在字符串后面追加“0”，如果为其右孩子，则在字符串后追加“1”。结束条件为没有父节点。然后将字符串倒过来存入结点中。

C++实现代码如下：

  1 #include<iostream>
  2 #include<string>
  3 using namespace std;
  4
  5 struct Node
  6 {
  7     double weight;
  8     string ch;
  9     string code;
 10     int lchild, rchild, parent;
 11 };
 12
 13 void Select(Node huffTree[], int *a, int *b, int n)//找权值最小的两个a和b
 14 {
 15     int i;
 16     double weight = 0; //找最小的数
 17     for (i = 0; i <n; i++)
 18     {
 19         if (huffTree[i].parent != -1)     //判断节点是否已经选过
 20             continue;
 21         else
 22         {
 23             if (weight == 0)
 24             {
 25                 weight = huffTree[i].weight;
 26                 *a = i;
 27             }
 28             else
 29             {
 30                 if (huffTree[i].weight < weight)
 31                 {
 32                     weight = huffTree[i].weight;
 33                     *a = i;
 34                 }
 35             }
 36         }
 37     }
 38     weight = 0; //找第二小的数
 39     for (i = 0; i < n; i++)
 40     {
 41         if (huffTree[i].parent != -1 || (i == *a))//排除已选过的数
 42             continue;
 43         else
 44         {
 45             if (weight == 0)
 46             {
 47                 weight = huffTree[i].weight;
 48                 *b = i;
 49             }
 50             else
 51             {
 52                 if (huffTree[i].weight  < weight)
 53                 {
 54                     weight = huffTree[i].weight;
 55                     *b = i;
 56                 }
 57             }
 58         }
 59     }
 60     int temp;
 61     if (huffTree[*a].lchild < huffTree[*b].lchild)  //小的数放左边
 62     {
 63         temp = *a;
 64         *a = *b;
 65         *b = temp;
 66     }
 67 }
 68
 69 void Huff_Tree(Node huffTree[], int w[], string ch[], int n)
 70 {
 71     for (int i = 0; i < 2 * n - 1; i++) //初始过程
 72     {
 73         huffTree[i].parent = -1;
 74         huffTree[i].lchild = -1;
 75         huffTree[i].rchild = -1;
 76         huffTree[i].code = "";
 77     }
 78     for (int i = 0; i < n; i++)
 79     {
 80         huffTree[i].weight = w[i];
 81         huffTree[i].ch = ch[i];
 82     }
 83     for (int k = n; k < 2 * n - 1; k++)
 84     {
 85         int i1 = 0;
 86         int i2 = 0;
 87         Select(huffTree, &i1, &i2, k); //将i1，i2节点合成节点k
 88         huffTree[i1].parent = k;
 89         huffTree[i2].parent = k;
 90         huffTree[k].weight = huffTree[i1].weight + huffTree[i2].weight;
 91         huffTree[k].lchild = i1;
 92         huffTree[k].rchild = i2;
 93     }
 94 }
 95
 96 void Huff_Code(Node huffTree[], int n)
 97 {
 98     int i, j, k;
 99     string s = "";
100     for (i = 0; i < n; i++)
101     {
102         s = "";
103         j = i;
104         while (huffTree[j].parent != -1) //从叶子往上找到根节点
105         {
106             k = huffTree[j].parent;
107             if (j == huffTree[k].lchild) //如果是根的左孩子，则记为0
108             {
109                 s = s + "0";
110             }
111             else
112             {
113                 s = s + "1";
114             }
115             j = huffTree[j].parent;
116         }
117         cout << "字符 " << huffTree[i].ch << " 的编码：";
118         for (int l = s.size() - 1; l >= 0; l--)
119         {
120             cout << s[l];
121             huffTree[i].code += s[l]; //保存编码
122         }
123         cout << endl;
124     }
125 }
126
127 string Huff_Decode(Node huffTree[], int n,string s)
128 {
129     cout << "解码后为：";
130     string temp = "",str="";//保存解码后的字符串
131     for (int i = 0; i < s.size(); i++)
132     {
133         temp = temp + s[i];
134         for (int j = 0; j < n; j++)
135         {
136             if (temp == huffTree[j].code)
137             {
138                 str=str+ huffTree[j].ch;
139                 temp = "";
140                 break;
141             }
142             else if (i == s.size()-1&&j==n-1&&temp!="")//全部遍历后没有
143             {
144                 str= "解码错误！";
145             }
146         }
147     }
148     return str;
149 }
150
151 int main()
152 {
153     //编码过程
154     const int n=5;
155     Node huffTree[2 * n];
156     string str[] = { "A", "B", "C", "D", "E"};
157     int w[] = { 30, 30, 5, 20, 15 };
158     Huff_Tree(huffTree, w, str, n);
159     Huff_Code(huffTree, n);
160     //解码过程
161     string s;
162     cout << "输入编码：";
163     cin >> s;
164     cout << Huff_Decode(huffTree, n, s)<< endl;;
165     system("pause");
166     return 0;
167 }

运行结果如下：