哈夫曼树遍历求WPL和哈夫曼编码C语言--For初学者

这篇文章使用纯c来写的，实现了生成哈夫曼树、求WPL和生成哈夫曼编码的应用，思路是，先定义一个结构体如下

typedef struct node
{
    int weight;
    struct node *lchild,*rchild;
    struct node *next;
}HuffNode;

先生成单链表（用next链接），还存储输入的权值（weight），单链表无头结点（因为最后要转化成二叉树，所以不用头结点），而且每一次节点的插入都使单链表保持递增的状态（为生成哈夫曼树做准备）。
计算WPL用到简单的递归，如下

int CalcWPL(HuffNode *huff,int wpl)
{
    HuffNode *p = huff;
    if(!p)
        return 0;
    else
    {
        if(!p->rchild&&!p->rchild)
            return p -> weight*wpl;
        else
            return CalcWPL(p->lchild,wpl+1) + CalcWPL(p->rchild,wpl+1);
    }
}

在计算WPL的代码上，稍作改动，就可以生成哈夫曼编码，如下

void HuffCode(HuffNode *huff,int len)
{
    HuffNode *p = huff;
    static int a[MAX];
    int i;
    if(p)
    {
        if(!p->lchild && !p->rchild)
        {
            printf("%d:",p->weight);

            for(i = 0;i< len;i++)
                printf("%d",a[i]);
            printf("\n");
        }
        else
        {
            a[len] = 0;
            HuffCode(p->lchild,len+1);
            a[len] = 1;
            HuffCode(p->rchild,len+1);
        }
    }
}

左孩子（lchild）和右孩子（rchild）是为生成二叉树准备的。
无头有序单链表的生成（就是链接权值），代码如下

void CreatUpLink(HuffNode **huff,int n)
{
    HuffNode *pre,*p ,*s,*head = (*huff);
    int x;
    scanf("%d",&x);
    s = malloc(sizeof(HuffNode));
    s -> lchild = NULL;
    s -> rchild = NULL;
    s -> weight = x;
    s -> next = NULL;
    head = s;
    n--;
    while(n--)
    {
        pre = p = head;
        scanf("%d",&x);
        s = malloc(sizeof(HuffNode));
        s -> lchild = NULL;
        s -> rchild = NULL;
        s -> weight = x;
        if(p->weight > x)
        {
            s -> next = p;
            head = s;
        }
        else
        {
            while(p&&p->weight < x)
                {
                    pre = p;
                    p = p->next;
                }
                s -> next = pre->next;
                pre -> next = s;
        }
    }
    (*huff) = head;
}

生成单链表是生成二叉树的基础，代码如下

void HuffTree(HuffNode **huff)
{
    HuffNode *pn1 ,*pn2 ,*p = *huff,*s = NULL,*q = NULL,*pre = NULL,*pr = NULL;
    if(!p->next)
        return ;
    while(p)
    {
        pn1 = p ;
        pn2 = pn1 -> next;
        pre = q = pn2 -> next ;
        s = malloc(sizeof(HuffNode));
        s -> lchild = pn1;
        s -> rchild = pn2;
        s -> weight = pn1 -> weight + pn2 -> weight;
        s ->next = NULL;
      if(!pn2 -> next)
      {
          s -> next = NULL;
          pn2 -> next = s;
          (*huff) = s;
          return;
      }
        if(pn2 -> next -> weight > s->weight)
        {
            s -> next = pn2 -> next;
            pn2 ->next = s;
        }
        else
        {
            while(q && q->weight < s -> weight)
                {
                    pre = q;
                    q = q->next;
                }
                s -> next = pre->next;
                pre -> next = s;
        }
        pr = pn2;
        p = pn2 -> next;
    }
    (*huff) = pr;
}

以上是重要的模块，主函数没有写，读者可以自行编写，我提供的代码仅供参考。
下面是全部的代码，编辑环境是Code::Blocks。

#include 
#include 

#define MAX 20
//201612-4
/* * * * * * * * * * * * * * * *
//测试数据
4
1 3 5 7
29

8
7 19 2 6 32 3 21 10
261
* * * * * * * * * * * * * * * */
typedef struct node
{
    int weight;
    struct node *lchild,*rchild;
    struct node *next;
}HuffNode;


void HuffTree(HuffNode **);
void CreatUpLink(HuffNode **,int);
void InitLink(HuffNode**);
void PrintNode(HuffNode**);
void PrePrint(HuffNode *);
int CalcWPL(HuffNode *,int);
void HuffCode(HuffNode *,int);
int main()
{
    int wpl = 0;
    HuffNode *huff;
    int n;
    scanf("%d",&n);
    CreatUpLink(&huff,n);
    PrintNode(&huff);
    HuffTree(&huff);
    printf("\nPreorder :\n");
    PrePrint(huff);
    wpl = CalcWPL(huff,0);
    printf("\n\nWPL = %d\n",wpl);
    printf("\nHuffCode:\n");
    HuffCode(huff,0);
    return 0;
}
int CalcWPL(HuffNode *huff,int wpl)
{
    HuffNode *p = huff;
    if(!p)
        return 0;
    else
    {
        if(!p->rchild&&!p->rchild)
            return p -> weight*wpl;
        else
            return CalcWPL(p->lchild,wpl+1) + CalcWPL(p->rchild,wpl+1);
    }
}
void HuffCode(HuffNode *huff,int len)
{
    HuffNode *p = huff;
    static int a[MAX];
    int i;
    if(p)
    {
        if(!p->lchild && !p->rchild)
        {
            printf("%d:",p->weight);

            for(i = 0;i< len;i++)
                printf("%d",a[i]);
            printf("\n");
        }
        else
        {
            a[len] = 0;
            HuffCode(p->lchild,len+1);
            a[len] = 1;
            HuffCode(p->rchild,len+1);
        }
    }
}
void PrePrint(HuffNode *huff)
{
    HuffNode *p = huff;
    if(p)
    {
        printf("%d\t",p->weight);
        PrePrint(p->lchild);
        PrePrint(p->rchild);
    }
}
void PrintNode(HuffNode **huff)
{
    HuffNode *p = (*huff);
    while(p)
    {
        printf("%d\t",p->weight);
        p = p->next;
    }
    putchar('\n');
}
void InitLink(HuffNode **huff)
{
    (*huff) = NULL;
}
void CreatUpLink(HuffNode **huff,int n)
{
    HuffNode *pre,*p ,*s,*head = (*huff);
    int x;
    scanf("%d",&x);
    s = malloc(sizeof(HuffNode));
    s -> lchild = NULL;
    s -> rchild = NULL;
    s -> weight = x;
    s -> next = NULL;
    head = s;
    n--;
    while(n--)
    {
        pre = p = head;
        scanf("%d",&x);
        s = malloc(sizeof(HuffNode));
        s -> lchild = NULL;
        s -> rchild = NULL;
        s -> weight = x;
        if(p->weight > x)
        {
            s -> next = p;
            head = s;
        }
        else
        {
            while(p&&p->weight < x)
                {
                    pre = p;
                    p = p->next;
                }
                s -> next = pre->next;
                pre -> next = s;
        }
    }
    (*huff) = head;
}
void HuffTree(HuffNode **huff)
{
    HuffNode *pn1 ,*pn2 ,*p = *huff,*s = NULL,*q = NULL,*pre = NULL,*pr = NULL;
    if(!p->next)
        return ;
    while(p)
    {
        pn1 = p ;
        pn2 = pn1 -> next;
        pre = q = pn2 -> next ;
        s = malloc(sizeof(HuffNode));
        s -> lchild = pn1;
        s -> rchild = pn2;
        s -> weight = pn1 -> weight + pn2 -> weight;
        s ->next = NULL;
      if(!pn2 -> next)
      {
          s -> next = NULL;
          pn2 -> next = s;
          (*huff) = s;
          return;
      }
        if(pn2 -> next -> weight > s->weight)
        {
            s -> next = pn2 -> next;
            pn2 ->next = s;
        }
        else
        {
            while(q && q->weight < s -> weight)
                {
                    pre = q;
                    q = q->next;
                }
                s -> next = pre->next;
                pre -> next = s;
        }
        pr = pn2;
        p = pn2 -> next;
    }
    (*huff) = pr;
}

运行结果图不附上了，读者可自行运算，本文只是用C语言来提供一种方法。
作者能力有限，难免有bug，欢迎大神评论指教。