假設在查找的過程中無法找到葉子節點，則報文有錯誤。

四、赫夫曼樹構造、編碼、譯碼代碼例如以下

1、我們須要兩個結構體，一個是赫夫曼樹節點的結構體。還有一個是鏈表節點的結構體：

typedef struct Node
{
	int weight;
	key_type key;
	struct Node *lchild, *rchild;
}HFMNode,*HFMTree;
/*用於鏈表的結構體*/
typedef struct link_node
{
	HFMTree data;
	struct link_node *next;
}LNode,*Link;

void init_link(Link *head);//初始化鏈表
void insert_link(Link head, HFMTree hfm);//向鏈表中插入一個元素，並依照權重排序
int delete_link(Link head,HFMTree *hfm);//依次刪除鏈表中的數據。成功返回1，失敗返回0
/*創建赫夫曼樹,str為keyword，w為相應的權重*/
int creat_hfmTree(HFMTree *root,char str[],int w[]);
/*獲取赫夫曼編碼表，存儲在數組code中*/
void hfmTree_code(HFMTree head, int a,char code[]);
/*譯碼,譯碼結果存儲在decode數組中,code輸入的報文*/
int hfmTree_decode(HFMTree head,const char code[],char decode[]);
3、總體代碼例如以下：

#include <iostream>
#include <assert.h>
typedef char key_type;
/*用於赫夫曼樹的結構體*/

using namespace std;

typedef struct Node
{
	int weight;
	key_type key;
	struct Node *lchild, *rchild;
}HFMNode,*HFMTree;
/*用於鏈表的結構體*/
typedef struct link_node
{
	HFMTree data;
	struct link_node *next;
}LNode,*Link;
/*對鏈表的操作*/
void init_link(Link *head);//初始化鏈表
void insert_link(Link head, HFMTree hfm);//向鏈表中插入一個元素。並依照權重排序
int delete_link(Link head,HFMTree *hfm);//依次刪除鏈表中的數據，成功返回1。失敗返回0
/*創建赫夫曼樹,str為keyword，w為相應的權重*/
int creat_hfmTree(HFMTree *root,char str[],int w[]);
/*獲取赫夫曼編碼表，存儲在數組code中*/
void hfmTree_code(HFMTree head, int a,char code[]);
/*譯碼,譯碼結果存儲在decode數組中,code輸入的報文*/
int hfmTree_decode(HFMTree head,const char code[],char decode[]);
int main()
{
	HFMTree root;
	char str[] = "abcdefg";
	int w[] = { 12, 18, 36, 79,85,32,40};
	creat_hfmTree(&root, str, w);
	
	char code[1024] = { 0 };//用來存放編碼表
	hfmTree_code(root, 1,code);
	cout <<"編碼結果為："<<endl<< code << endl;
	
	char decode[90] = { 0 };
	hfmTree_decode(root, "00001100010010100111011", decode);
	cout <<"譯碼結果為："<<endl<< decode << endl;

}

void init_link(Link *head)
{
	(*head) = (Link)malloc(sizeof(LNode));
	(*head)->next = NULL;
	(*head)->data = NULL;
}

void insert_link(Link head, HFMTree hfm)
{
	assert(head != NULL);
	/*先構造鏈表節點*/
	Link temp = (Link)malloc(sizeof(LNode));
	temp->next = NULL;
	temp->data = hfm;

	while (head->next != NULL && head->next->data->weight < hfm->weight)
	{
		head = head->next;
	}
	if (head->next == NULL)
	{
		head->next = temp;
	}
	else
	{
		temp->next = head->next;
		head->next = temp;
	}
}

int delete_link(Link head, HFMTree *hfm)
{
	assert(head != NULL);
	if (head->next == NULL)
		return 0;
	Link temp = head->next;
	head->next = temp->next;

	*hfm = temp->data;

	free(temp);
	return 1;
}

int creat_hfmTree(HFMTree *root, char str[], int w[])
{
	int n = strlen(str);
	HFMTree temp;

	Link head;
	init_link(&head);
	/*構造節點，依照權重的遞增順序插入到鏈表中*/
	for (int i = 0; i < n;i++)
	{
		/*構造節點*/
		temp = (HFMTree)malloc(sizeof(HFMNode));
		
		temp->key = str[i];
		temp->weight = w[i];
		temp->lchild = NULL;
		temp->rchild = NULL;

		insert_link(head, temp);
	}
	if (head->next == NULL)//鏈表中沒有元素
		return 0;
	/*從鏈表中取出兩個最小的節點構造赫夫曼樹*/
	HFMTree temp1, temp2, temp3;
	/*鏈表中存在1個元素則退出循環*/
	while ( delete_link(head,&temp1) && delete_link(head,&temp2) )
	{
		temp3 = (HFMTree)malloc(sizeof(HFMNode));

		temp3->weight = temp1->weight + temp2->weight;
		temp3->lchild = temp1;
		temp3->rchild = temp2;

		insert_link(head, temp3);
	}
	*root = temp1;
	return 1;
}

void hfmTree_code(HFMTree head, int a, char code[])
{
	static int i = 0;
	if (head != NULL)
	{
		if (head->lchild == NULL && head->rchild == NULL)//訪問到了葉子節點
		{
			code[i++] = head->key;
			code[i++] = ':';//在keyword後面加"："，其後面的"0"、"1"表示編碼
			int count = 0;
			/*對a做處理。a最前面的1要舍去*/
			while (a > 1)
			{
				if (a % 2 == 0)
					code[i++] = '0';
				else
					code[i++] = '1';
				a = a>>1;
				count++;
			}
			/*對字符串反轉，這樣才和我們的赫夫曼編碼一直*/
			strrev( code + i - count);
			/*keyword之間的編碼用空格分開*/
			code[i++] = ' ';
		}
		hfmTree_code(head->lchild, a * 2, code);
		hfmTree_code(head->rchild, a * 2 + 1, code);
	}
}

int hfmTree_decode(HFMTree head, const char code[], char decode[])
{
	assert(head != NULL);
	HFMTree root = head,pre;
	int i = 0;
	int j = 0;
	
	while (code[i] == '0' || code[i] == '1')
	{
		if (code[i] == '0')
			head = head->lchild;
		else
			head = head->rchild;
		if (head->rchild == NULL )//訪問到了葉子節點
		{
			decode[j] = head->key;
			j++;
			head = root;
		}
		i++;
	}
	if (code[i] != '\0')//沒有訪問到葉子節點
	{
		cout << "報文錯誤" << endl;
		return 0;
	}
	return 1;
}

赫夫曼樹的構建、編碼、譯碼解析