Queues are FIFO (first in first out) linear form, referred to as FIFO.
Suppose circular queues:
Team head: front
The tail: rear
Maximum size: queue size
Queue full: (rear + 1)% queue size == front
Common queue length is calculated: (rear - front + queue size)% queue size
Sample code storage structure
typedef int QElemType; / * type of data within the queue * /
/ * Sequential storage structure circular queue * /
typedef struct
{
QElemType date[MAXSIZE];
int front; / * head pointer * /
int rear; / * tail pointer, if the queue is not empty, a point to enqueue position * /
} SqQueue;
/ * Initialize an empty queue * /
int InitQueue（SqQueue *Q）
{
Q->front = 0；
Q->rear = 0;
return OK;
}
/ * Find a circular queue length * /
int QueueLenght（SqQueue *Q）
{
return （Q.rear - Q.front + MAXSIZE）% MAXSIZE;
}
/ * Enqueue operation circular queue * /
int EnQueue（SqQueue *Q， QElemType e）
{
if ((Q-> rear + 1)% MAXSIZE == Q-> front) / * * determined queue full /
return ERROR;
Q-> data [Q-> rear] = e; / * * a new element to the tail /
Q-> rear = (Q-> rear + 1)% MAXSIZE; / * pointer is moved one after the rear * /
/ * If you go to the last head array * /
return OK;
}
/ * Dequeue circular queue * /
int EnQueue（SqQueue *Q， QElemType *e）
{
if (Q-> rear == Q-> front) / * Analyzing queue is empty * /
return ERROR;
* E = Q-> data [Q-> front]; / * the head elements to e * /
Q-> front = (Q-> front + 1)% MAXSIZE; / * pointer moves back front a * /
/ * If you go to the last head array * /
return OK;
}