Data Structure-compliant FIFO queues (2)

I. Concept of queue

A queue is a special linear table that strictly follows the "first-in-first-out" principle.

Ii. Queue Basics

　　Like a stack, a queue only allows you to insert and delete elements at breakpoints. The basic operations include:

(1) initqueue (& Q); // Initialize an empty queue

(2) destroyqueue (& Q); // clear the queue

(3) queueempty (& Q); // The queue is empty.

(4) queuelength (& Q); // evaluate the queue length

(5) gethead (Q, & E); // obtain the first element.

(6) enqueue (& Q, e); // Insert a new element

(7) dequeue (& Q, & E); // deletes the team Header element.

(8) queuetraverse (Q, visit (); // each element calls the visit () function.

　　Queue classification: chain queue and cyclic queue

　　C language defines the blockchain format

Typedef struct qnode {elemtype data; struct qnode * Next;} qnode, * queueptr; typedef struct {queueptr front; // head pointer, pointing to the Header element queueptr rear; // team end pointer, point to team end element} linkqueue;

You can use an ordered table to store and define cyclic queues. The Code is as follows:

# Define maxqsize 100 // longest queue length typedef struct {elemtype * base; // storage space int front; // header pointer, pointing to the queue's Header element int rear; // tail pointer, pointing to the next position of the queue element} sqqueue;

Basic queue operations

(1) The purpose of initializing queue Q is to create a queue

void InitQueue(QUEUE *Q){    Q->front = -1;    Q->rear = -1;}

(2) The goal is to add a new element to the end of the team, which is equivalent to waiting in the last queue of the queue.

void EnQueue(QUEUE *Q, Elemtype elem){    if ((Q->rear+1)%MAX_QUEUE==Q->front)    {        exit(OVERFLOW);    }    else{        Q->rear = (Q->reasr + 1) % MAX_QUEUE;        Q->elem[Q->rear] = elem;    }}

(3) The goal of the team is to retrieve the first element and delete it at the same time so that the last element becomes the first element.

void DeQueue(QUEUE *Q, Elemtype *elem){    if (QueueEmpty(*Q))    {        exit("Queue is empty.");    }    else    {        Q->front = (Q->front + 1) % MAX_QUEUE;        *elem = Q->elem[Q->front];    }}

(4) obtain the first element of the queue. This element is removed from the queue header. If this element is not deleted, the queue header is still the element.

void GetFront(QUEUE *Q, Elemtype *elem){    if (QueueEmpty(*Q))    {        exit("Queue is empty.");    }    else    {        *elem = Q->elem[ (Q->front + 1) % MAX_QUEUE];    }}

(5) determine whether queue Q is empty

int QueueEmpty(Queue Q){    if (Q.front==Q.rear)    {        return TRUE;    }    else    {        return FALSE;    }}

　　Queue chain Storage

　　In C, the basic operation algorithm of chained queue is as follows:

(1) initialize queue Q. The algorithm code is as follows:

void InitQueue(QUEUE *Q){    Q->front = (LINKLIST*)malloc(sizeof(LINKLIST));    if (Q->front==NULL)     {        exit(ERROR);    }    Q->rear = Q->front;}

(2) team-up operations

void EnQueue(QUEUE *Q, Elemtype elem){    s = (LINKLIST*)malloc(sizeof(LINKLIST));    if (!s)    {        exit(ERROR);    }    s->elem = elem;    s->next = NULL;    Q->rear->next = s;    Q->rear = s;}

(3) team-out operations

void DeQueue(QUEUE *Q, Elemtype *elem){    if (QueueEmpty(*Q))    {        exit(ERROR);    }    else    {        *elem = Q->front->next->elem;        s = Q->front->next;        Q->front->next = s->next;        Q->front = (Q->front + 1) % MAX_QUEUE;        free(s);    }}

(4) obtain the element of the team Header

void GetFront(QUEUE Q, Elemtype *elem){    if (QueueEmpty(Q))    {        exit(ERROR);    }    else    {        *elem = Q->front->next->elem;    }}

(5) determine whether queue Q is empty

void QueueEmpty(QUEUE Q){    if (Q->front==Q->rear)    {        return TRUE;    }    else    {        return FALSE;    }}

Iii. instance Drill

Question about "add customer" Number

Code implementation:

Implementation result:

 

Data Structure-compliant FIFO queues (2)