进程出队

#include <malloc.h>
#include <stdio.h>
#include <string.h>

typedef struct processpcb
{	
	int id;			/*??*/
	struct processpcb *next;
}node;
node *creat(void)	//??
{
	node *head, *p1, *p2;
	int n = 0;

	printf("Input processpcb table:ID\n");
	p1 = p2 = (node*)malloc(sizeof(node));
	scanf("%d", &p1->id);
	
	head = NULL;
	while (p1->id > 0) {
		n = n+1;
		if (n == 1)
			head = p1;
		else
			p2->next = p1;
		p2 = p1;
		p1 = (node*)malloc(sizeof(node));
		scanf("%d", &p1->id);
	}
	p2->next = NULL;
	free (p1);
	return head;
}

void print(node *head)
{
	node *p;
	p = head;
	if (head != NULL)
		do {
			printf("%d\t", p->id);
			p = p->next;
		} while (p != NULL);
}

/*??????????*/
node *del(node *head,int pcb)	
{
	node *p, *q;
	p = head;
	
	if (!head)
		printf("not found!");
	else {
		if (p->id == pcb && !p->next) {	//???
			free(p);
			return NULL;
		} else if (p->id == pcb && p->next) {
			head = head->next;
			free(p);
			return head;
		} else {
			while (p && p->id != pcb) {
				q = p;
				p = p->next;
			}
			if (!p)
				printf("not found!");
			else {
				q->next = p->next;
				free(p);
				return head;
			}	
		}
	}	
}

int main(void)
{
	node *p;
 	int pcbid;
 	
 	p = creat();
 	printf("\ndel a processpcb\n");
 	scanf("%d",&pcbid);
 	printf("\ninit_processpcb queue is:\n");
 	print(p);
 	p = del(p,pcbid);
 	printf("\ndel_processpcb queue is:\n");
 	print(p);
 	
	return 0;
}