HuffmanTree的创建及编码

Marcky — Mon, 28 Sep 2009 09:49:00 GMT

typedef struct _HTNode {
    unsigned int weight;        /* 权值 */
    unsigned int parent;        /* 父节点索引 */
    unsigned int lchild;        /* 左孩子索引 */
    unsigned int rchild;        /* 右孩子索引 */
} HTNode, *HuffmanTree;         /* 动态分配数组存储哈夫曼树 */

typedef char **HuffmanCode;     /* 动态分配数组存储哈夫曼编码表 */

/* 从ht的1～n的节点中找出权值最小的两个节点，分别存于s1, s2中 */
void Select(HuffmanTree ht, int n, int *s1, int *s2)
{
    int i;

    *s1 = 0;
    *s2 = 0;
    /*设置s1, s2到开始两个parent等于0的节点位置*/
    for (i = 1; i <= n; ++i) {
        if (*s1 != 0 && *s2 != 0)
            break;

        if (ht[i].parent == 0)
            *s1 == 0 ? *s1 = i : *s2 = i;
    }
    /*找出ht中parent等于0，且权值最小的两个节点位置，分别存于s1, s2中*/
    for ( ; i <= n; ++i) {
        if (ht[i].parent != 0) continue;

        if ( (ht[*s1].weight > ht[*s2].weight) && (ht[*s1].weight > ht[i].weight))
            *s1 = i;
        else if ( (ht[*s2].weight > ht[*s1].weight) && (ht[*s2].weight > ht[i].weight))
            *s2 = i;
    }
}

/* 通过w存储的n个权值，来创建一颗哈夫曼树, ht_ptr指向这颗哈夫曼树 */
void CreateHuffmanTree(HuffmanTree *ht_ptr, int *w, int n)
{
    int m;
    int i;
    int s1, s2;
    HuffmanTree p;

    if (n <= 1) return;
    m = 2 * n - 1;              /* n个字符，需要2n-1个空间来存储整颗huffman tree */
    *ht_ptr = (HuffmanTree)malloc( (m + 1) * sizeof(HTNode)); /* 0号单元不用 */

    for (p = *ht_ptr + 1, i = 1; i <= n; ++i, ++p, ++w) { /* 初始化数组中前n个单元存储的字符 */
        p->weight = *w;
        p->parent = 0;
        p->lchild = 0;
        p->rchild = 0;
    }
    for ( ; i <= m; ++i, ++p) { /* 初始化数组中剩余的单元 */
        p->weight = 0;
        p->parent = 0;
        p->lchild = 0;
        p->rchild = 0;
    }

    for (i = n + 1; i <= m; ++i) {
        Select(*ht_ptr, i - 1, &s1, &s2);
        /* 设置s1, s2的父亲为i */
        (*ht_ptr + s1)->parent = i;
        (*ht_ptr + s2)->parent = i;
        /* 设置i的左孩子为s1, 右孩子为s2 */
        (*ht_ptr + i)->lchild = s1;
        (*ht_ptr + i)->rchild = s2;
        /* 设置i的权值为s1, s2之和 */
        (*ht_ptr + i)->weight = (*ht_ptr + s1)->weight + (*ht_ptr + s2)->weight;
    }
}

/* 对ht_ptr存储的哈夫曼树的n个叶子节点进行哈夫曼编码 */
void HuffmanCoding(HuffmanTree *ht_ptr, HuffmanCode *hc_ptr, int n)
{
    int i;
    int start;
    char *cd = NULL;

    *hc_ptr = (HuffmanCode)malloc( (n + 1) * sizeof(char *));

    cd = (char *)malloc(n * sizeof(char));
    cd[n - 1] = '\0';

    for (i = 1; i <= n; ++i) {
        start = n - 1;

        int current, father;
        for (current = i, father = (*ht_ptr + i)->parent; /* 从叶子节点开始，并取得父节点father */
             father != 0;                                 /* 父节点为0时及到达了根节点 */
             current = father, father = (*ht_ptr + father)->parent) { /* 逐渐向根节点靠拢 */
            if ( (*ht_ptr + father)->lchild == current) /* 当前节点为左孩子 */
                cd[--start] = '0';
            else
                cd[--start] = '1';

        }

        *(*hc_ptr + i) = (char *)malloc( (n - start) * sizeof(char));
        strcpy(*(*hc_ptr +i), &cd[start]);
    }
    free(cd);
}

Marcky 2009-09-28 17:49 发表评论

二叉树的创建及遍历（递归代码）

Marcky — Thu, 24 Sep 2009 14:33:00 GMT

typedef enum _STATUS {ERROR, OK} STATUS;

typedef struct _BiTNode {
    char data;
    struct _BiTNode *lchild;
    struct _BiTNode *rchild;
} BiTNode, *BiTree;

/*创建二叉树*/
STATUS CreateBiTree(BiTree *T)
{/*按先序次序输入二叉树节点的值，空格表示空树。*/
    char ch;

    scanf("%c", &ch);
    if (ch == ' ') {
        *T = NULL;
    } else {
        if ( !(*T = (BiTNode *)malloc(sizeof(BiTNode)))) exit(-1);
        (*T)->data = ch;                     //生成根节点
        CreateBiTree(&((*T)->lchild));       //构造左子树
        CreateBiTree(&((*T)->rchild));       //构造右子树
    }
    return OK;
}

/*中序遍历二叉树*/
STATUS InOrderTraverse(BiTree *T)
{
    if (*T) {
        if (InOrderTraverse(&((*T)->lchild)))
            printf("%c ", (*T)->data);
            if (InOrderTraverse(&((*T)->rchild)))
                return OK;
        return ERROR;
    } else {
        return OK;
    }
}

Marcky 2009-09-24 22:33 发表评论

C++博客-键盘上的舞者-随笔分类-数据结构和算法

HuffmanTree的创建及编码

二叉树的创建及遍历（递归代码）