优先队列实现Huffman树

 优先队列实现Huffman树主要在构造m-1个内部结点是提高了构建的效率

/*
*优先队列实现哈夫曼树:哈夫曼树外部结点的个数为m,内部结点为m-1，所以总结点树为2m-1
*/
#include
#include

#define MAX_PQ_SIZE 100
#define MAX_NUM 6

/*Haffuman tree data type define*/
struct HtNode		/*哈夫曼树结点的结构*/
{
	int ww;			/*以该结点为根的子树中所有外部结点的加权和*/
	int parent,llink,rlink;	
};
struct HtTree		/*哈夫曼树结构*/
{
	int m;			/*外部结点的个数*/
	int root;		/*哈夫曼树根在数组中的下标*/
	struct HtNode *ht; /*存放2*m-1个结点的数组*/
};
typedef struct HtTree *PHtTree;

typedef struct HtNode* element_type;
/*Priority tree datatype define*/
 struct heap_struct
{
	/*Maximum # that can fit in the heap*/
	unsigned int max_heap_size;

	/*Crurrent # of elements in the head*/
	unsigned int size;

	element_type *elements;
};

typedef struct heap_struct*PRIORITY_QUEUE;

PRIORITY_QUEUE create_pq(unsigned int max_elements)
{
	PRIORITY_QUEUE H;

	if(max_elements>MAX_PQ_SIZE)
	{
		printf("Priority queue size is too large\n");
		return NULL;
	}
		

	H=(PRIORITY_QUEUE)malloc(sizeof(struct heap_struct));
	if(NULL==H)
	{
		printf("Out of space!\n");
		return NULL;
	}

	/*Allocate the array + one extra for sentinel*/
	H->elements=(element_type*)malloc((max_elements+1)*sizeof(element_type));
	if(NULL==H->elements)
	{
		printf("Out of space!\n");
		free(H);
		return NULL;
	}
	H->max_heap_size=max_elements;
	H->size=0;
	H->elements[0]=NULL;

	return H;	
}
bool isEmptyPriorityQueue(PRIORITY_QUEUE H)
{
	return H->size==0;
}
/*H->elements[0] is a sentinel*/
void enQueue(element_type x,PRIORITY_QUEUE H)
{
	unsigned int i;

	if(H->size==H->max_heap_size)
		printf("Priority queue is full\n");
		
	else
	{
		i=++H->size; /*the position of new element*/

		while((i/2)!=0)/*compare with the value of the parent node*/
		{
			if((*(H->elements[i/2])).ww>(*x).ww)/*通过间接访问运算与父结点的值进行比较*/
			{
				H->elements[i]=H->elements[i/2];/*swap down*/
				i=i/2;
			}
			else
				break;		
		}
		H->elements[i]=x;	/*the final position*/
	}
}
element_type deQueue(PRIORITY_QUEUE H)
{
	unsigned int i,child;
	element_type min_element,last_element;

	if(0==H->size)
	{
		printf("Priority queue if empty\n");
		return H->elements[0];
	}
	min_element=H->elements[1];
	last_element=H->elements[H->size--];
	
	for(i=1;i*2<=H->size;i=child)
	{
		/*find smaller child*/
		child=i*2;
		if((child!=H->size)&&((*H->elements[child+1]).ww<(*H->elements[child]).ww))
			child++;
		/*percolate one level*/
		if((*last_element).ww>(*H->elements[child]).ww)
			H->elements[i]=H->elements[child];/*child move up*/
		else
			break;/*is the smallest*/
	}
	H->elements[i]=last_element;/*set here*/

	return min_element;
}
element_type topPriorityQueue(PRIORITY_QUEUE H)
{
	if(isEmptyPriorityQueue(H))
	{
		printf("Priority queue is empty!\n");
		return H->elements[0];
	}
	else
		return H->elements[1];
}
PHtTree huffman(int m,int *w)/*构造具有m个外部结点的哈夫曼树*/
{
	PHtTree pht;/*declare a pointer to Huffman tree*/
	PRIORITY_QUEUE pq;/*declare a pointer to priority queue*/
	int i;
	struct HtNode *x1,*x2;/*two pointer of HtNode*/

	pht=(PHtTree)malloc(sizeof(struct HtTree));
	if(NULL==pht)
	{
		printf("Out of space!\n");
		return pht;
	}
	pht->ht=(struct HtNode*)malloc(sizeof(struct HtNode)*(2*m-1));
	if(NULL==pht)
	{
		printf("Out of space!\n");
		return pht;
	}
	for(i=0;i<2*m-1;i++)/*the array(ht) initializtion*/
	{
		pht->ht[i].llink=-1;
		pht->ht[i].rlink=-1;
		pht->ht[i].parent=-1;
		if(iht[i].ww=w[i];
		else
			pht->ht[i].ww=-1;
	}
	pq=create_pq(MAX_NUM);/*分配优先队列空间 */
	for(i=0;iht+i,pq);/*注意：是将结点的地址加入优先队列*/
	}
	/* 构造哈夫曼树，每循环一次构造出一个内部结点（一棵子树） */
	for(i=0;iparent=m+i;/*填入指向父节点的下标信息*/
        x2->parent=m+i;
        pht->ht[m+i].ww=x1->ww+x2->ww;    /*填入父节点的权重*/   
        pht->ht[m+i].llink=x1->llink;/*填入父节点的左右儿子字段信息*/
        pht->ht[m+i].rlink=x2->rlink;
       
        enQueue(pht->ht+m+i,pq);/*将新构造的节点的地址插入优先队列*/
    }
	pht->root=2*m-2;/*指向根节点*/

	for(i=2*m-2;i>=0;i--)/*print Huffman tree*/
		printf("No.%2d, value =%3d, lLink =%2d, rLink =%2d, parent =%2d\n",
						i,pht->ht[i].ww,pht->ht[i].llink,pht->ht[i].rlink,pht->ht[i].parent);
		
	return pht;

}
int main()
{
	int weight[MAX_NUM]={12,3,56,7,8,32};

	huffman(MAX_NUM,weight);

	return 0;
}