C Language single chain queue representation and implementation Example _c language

1. Overview:

C-language queues (queue), which refers to the first out (FIFO, first-in-first-out) of the linear table. In a specific application, a linked list or array is usually used for implementation. Queues allow insertions only at the back end (called rear) and are removed at the front end (called the front).

The single chain queues use linked lists as the basic data results, so there is no problem of pseudo overflow, queue length is not limited. But the time to insert and read is higher

2. Instance code:

/* Single Chain queue----chained storage structure of queue/typedef struct QNODE {qelemtype data;
struct Qnode *next;
}qnode,*queueptr;
typedef struct {queueptr front,rear;/* team head, Team tail pointer * *}LINKQUEUE;
 /* Chain Queue Basic Operations (9)/void Initqueue (Linkqueue *q) {/* Constructs an empty queue Q/q->front=q->rear=malloc (sizeof (Qnode)); if (!
 Q->front) exit (OVERFLOW);
q->front->next=null;
  } void Destroyqueue (Linkqueue *q) {/* Destroy queue Q (either null or void) */while (Q->front) {q->rear=q->front->next;
  Free (Q->front);
 q->front=q->rear;
 } void Clearqueue (Linkqueue *q) {/* The Q is cleared as an empty queue */Queueptr p,q;
 q->rear=q->front;
 p=q->front->next;
 q->front->next=null;
  while (p) {q=p;
  p=p->next;
 Free (q);
 The Status queueempty (linkqueue q) {/* If q is an empty queue, returns True, otherwise returns false */if (q.front->next==null) return true;
else return FALSE;
 The int queuelength (Linkqueue Q) {* * asks for the length of the queue */int i=0;
 Queueptr p;
 P=q.front;
  while (q.rear!=p) {i++;
 p=p->next;
return i; Status gethead_q (Linkqueue q,qElemtype *e) {/* If the queue is not empty, then use E to return the team head element of Q, and return OK, otherwise return error * * * QUEUEPTR p;
 if (q.front==q.rear) return ERROR;
 p=q.front->next;
 *e=p->data;
return OK;
 } void EnQueue (Linkqueue *q,qelemtype e) {//* insert element E As Q of the new team tail element */queueptr p= (queueptr) malloc (sizeof (Qnode));
 if (!p)/* Storage Allocation failed/exit (OVERFLOW);
 p->data=e;
 p->next=null;
 q->rear->next=p;
q->rear=p;
 Status dequeue (linkqueue *q,qelemtype *e) {/* If the queue is not empty, delete Q's team head element, return its value with E, and return OK, otherwise return error * * * QUEUEPTR p;
 if (q->front==q->rear) return ERROR; p=q->front;
 /* Point head node * * *e=p->data; q->front=p->next;
 /* Pick the head node */if (q->rear==p) q->rear=q->front;
 Free (p);
return OK;
 } void Queuetraverse (Linkqueue q,void (*VI) (Qelemtype)) {/* calls function VI ()/queueptr p for each element in queue Q from Team head to Team tail;
 p=q.front->next;
  while (p) {VI (P->DATA);
 p=p->next;
printf ("\ n"); }