双链表优先队列ADT的实现与测试

源代码如下：

#include <stdlib.h>
#include <stdio.h>
typedef struct pq* PQ;
typedef struct PQnode* PQlink;
struct Item{int data;char c;};
struct PQnode{Item key;PQlink prev,next;};
struct pq{PQlink head,tail;};

PQ PQinit(){
	PQ pq = (PQ)malloc(sizeof*pq);
	PQlink h = (PQlink)malloc(sizeof*h),
			t = (PQlink)malloc(sizeof*t);
	h->prev = t; h->next = t;
	t->next = h; t->prev = h;   //头尾指针不存放数据
	pq->head = h; pq->tail = t;
	return pq;
}

int PQempty(PQ pq){
	return pq->head->next->next == pq->head;
}

PQlink PQinsert(PQ pq, Item v){
	PQlink t = (PQlink)malloc(sizeof *t);
	//设置节点t的相关信息
	t->key = v;t->next=pq->head->next;t->prev=pq->head;
	//维护双链表
	t->next->prev=t;pq->head->next = t;
	return t;
}

Item PQdelmax(PQ pq){
	Item max;struct PQnode *t,*x=pq->head->next;
	for(t=x; t->next!=pq->head;t=t->next)
		if(t->key.data>x->key.data) x = t;
	max =x->key;
	//维护双链表
	x->next->prev=x->prev;x->prev->next=x->next;
	free(x);return max;
}

void PQchange(PQ pq, PQlink x, Item v){
	x->key=v;
}

void PQdelete(PQ pq, PQlink x){
	x->next->prev=x->prev;x->prev->next=x->next;
	free(x);
}

//并不破坏b的结构？？！！（<span style="color:#ff0000;">求答疑</span>） 将b队列追加在a尾处
void PQjoin(PQ a, PQ b){
	a->tail->prev->next = b->head->next;
	b->head->next->prev = a->tail->prev;
	a->head->prev = b->tail;
	b->tail->next = a->head;
	free(a->tail);free(b->head);
}

void test(){
	PQ pq = PQinit();
	PQ pq2 = PQinit();
	Item a = {2,'a'};
	Item b = {3,'b'};
	Item c = {1,'c'};
	PQinsert(pq,a);PQinsert(pq2,b);PQinsert(pq2,c);
	printf("%d %d \n",pq2->head->next->key.data,pq2->head->next->next->key.data);
	PQjoin(pq,pq2); //
	printf("%d %d \n",pq2->head->next->key.data,pq2->head->next->next->key.data);
	Item d = {21,'d'};
	PQchange(pq,pq->head->next,d);
	PQdelete(pq,pq->head->next->next);
	while(!PQempty(pq)){
		printf("%d \n",PQdelmax(pq).data);
	}
}

main(){
	test();
}

运行结果

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