C语言构造哈夫曼编码

首先我们定义两个结构体,一个用于定义哈夫曼树的结点,一个用来定义每个叶子结点的哈夫曼编码.

typedef struct
{
    char data;          //结点值
    double weight;          //权重
    int parent;         //父亲结点
    int lchild;         //左孩子结点
    int rchild;         //右孩子结点
} HTNode;               //哈夫曼树的结点类型

typedef struct
{
    char cd[MAXN];          //存放当前结点的哈夫曼码
    int start;          //用来存储当前叶子结点哈夫曼编码的首地址
} HCode;

构造哈夫曼树,传递数组参数.
定义左右结点,并循环从数组里面找到最小和次小结点.

void CreateHTree(HTNode ht[], int n)    //构造哈夫曼树
{
    int i, j, lnode, rnode;
    double min1, min2;
    for (i = 0; i <= 2 * n - 2; i++)        //所有结点的相关域置初值-1
        ht[i].parent = ht[i].lchild = ht[i].rchild = -1;
    for (i = n; i <= 2 * n - 2; i++)        //构造哈夫曼树
    {
        min1 = min2 = 32767; //lnode和rnode为最小权值的两个结点的下标
        lnode = rnode = -1;
        for (j = 0; j <= i - 1; j++)        //在ht[]中找权值最小的两个结点 ht[]就相当于那个二叉树集合
            if (ht[j].parent == -1) //只在根结点中查找
            {
                if (ht[j].weight < min1)
                {
                    min2 = min1;
                    rnode = lnode;
                    min1 = ht[j].weight;
                    lnode = j;
                }
                else if (ht[j].weight < min2)
                {
                    min2 = ht[j].weight;
                    rnode = j;
                }
            }
        ht[i].weight = ht[lnode].weight + ht[rnode].weight;
        ht[i].lchild = lnode;
        ht[i].rchild = rnode; //ht[i]作为父亲结点
        ht[lnode].parent = i;
        ht[rnode].parent = i; //将选出的那两个最小和次小结点的父亲修改为i.
    }
}

#include<stdio.h>
#define MAXN 101
typedef struct
{
    char data;          //结点值
    double weight;          //权重
    int parent;         //父亲结点
    int lchild;         //左孩子结点
    int rchild;         //右孩子结点
} HTNode;               //哈夫曼树的结点类型

typedef struct
{
    char cd[MAXN];          //存放当前结点的哈夫曼码
    int start;          //用来存储当前叶子结点哈夫曼编码的首地址
} HCode;

void CreateHTree(HTNode ht[], int n)    //构造哈夫曼树
{
    int i, j, lnode, rnode;
    double min1, min2;
    for (i = 0; i <= 2 * n - 2; i++)        //所有结点的相关域置初值-1
        ht[i].parent = ht[i].lchild = ht[i].rchild = -1;
    for (i = n; i <= 2 * n - 2; i++)        //构造哈夫曼树
    {
        min1 = min2 = 32767; //lnode和rnode为最小权值的两个结点的下标
        lnode = rnode = -1;
        for (j = 0; j <= i - 1; j++)        //在ht[]中找权值最小的两个结点 ht[]就相当于那个二叉树集合
            if (ht[j].parent == -1) //只在根结点中查找
            {
                if (ht[j].weight < min1)
                {
                    min2 = min1;
                    rnode = lnode;
                    min1 = ht[j].weight;
                    lnode = j;
                }
                else if (ht[j].weight < min2)
                {
                    min2 = ht[j].weight;
                    rnode = j;
                }
            }
        ht[i].weight = ht[lnode].weight + ht[rnode].weight;
        ht[i].lchild = lnode;
        ht[i].rchild = rnode; //ht[i]作为父亲结点
        ht[lnode].parent = i;
        ht[rnode].parent = i; //将选出的那两个最小和次小结点的父亲修改为i.
    }
}
void CreateHCode(HTNode ht[], HCode hcd[], int n) //根据哈夫曼树求哈夫曼编码
{
    int i, f, c;
    for (i = 0; i < n; i++)     //产生每个叶子结点的哈夫曼编码
    {
        hcd[i].start = n - 1;   //哈夫曼编码从cd的n-1下标开始放置
        c = i;              //c初值指要产生编码的结点
        f = ht[i].parent;
        while (f != -1)     //循环直到无父亲结点即到达树根结点
        {
            if (ht[f].lchild == c) //当前结点是父亲结点的左孩子结点
                hcd[i].cd[hcd[i].start--] = '0';
            else        //当前结点是父亲结点的右孩子结点
                hcd[i].cd[hcd[i].start--] = '1';
            c = f;
            f = ht[f].parent;   //再对父亲结点进行同样的操作
        }
        hcd[i].start++; //start指向哈夫曼编码最开始的二进制位
    }
}
void dispHCode(HTNode ht[], HCode hcd[], int n) //输出哈夫曼编码
{
    int i, j;
    for (i = 0; i < n; i++)
    {
        printf("  %c:", ht[i].data);
        for (j = hcd[i].start; j < n; j++)
            printf("%c", hcd[i].cd[j]);
        printf("\n");
    }
}


int main()
{
    int n = 5;
    HTNode ht[2 * MAXN - 1];
    HCode hcd[MAXN];

    ht[0].data = 'a';
    ht[0].weight = 4;       //为哈夫曼树添加n个叶子结点

    ht[1].data = 'b';
    ht[1].weight = 2;

    ht[2].data = 'c';
    ht[2].weight = 1;

    ht[3].data = 'd';
    ht[3].weight = 7;

    ht[4].data = 'e';
    ht[4].weight = 3;

    CreateHTree(ht, n);             //建立哈夫曼树
    CreateHCode(ht, hcd, n);            //求哈夫曼编码
    printf("产生的哈夫曼编码如下:\n");
    dispHCode(ht, hcd, n);              //输出哈夫曼编码
    getchar();
    return 0;
}