Description Language c - a circular queue and the queue chain

I really do not like writing code

Queue features

• FIFO, which can only insert elements from the tail, removing elements from the team head

Storage Structure queue

#include<stdio.h>
#include <stdlib.h>
#include<malloc.h>
typedef struct QNode
{
    int date;
    struct QNode *next;
}QNode ,*QueuePtr;

typedef  struct
{
    int size; //记录队列长度
    QueuePtr front; //头指针
    QueuePtr rear;  //尾指针
}LinkQueue;
//初始化
void InitQueue(LinkQueue *Q)
{
    Q->front=Q->rear=(QNode *)malloc(sizeof(QNode));
    if(!Q->front)
      exit(0);
    Q->rear->next=NULL;
    Q->size=0;
}
//在队尾插入元素
void InsertQueue(LinkQueue *Q,int e)
{
    QNode *p;
    p=(QueuePtr)malloc(sizeof(QNode));
    if(p==NULL)
      exit(0);
    p->date=e;
    Q->rear->next=p;
    Q->rear=p;
    Q->rear->next=NULL;
    Q->size++;
}
//删除队头元素
void Pop_Queue(LinkQueue *Q)
{
    Q->front=Q->front->next;
    free(Q->front);
    Q->size--;
}
//向队列输入数据
void Push_Queue(LinkQueue *Q)
{
    int e;
    QNode *p=NULL;
    printf("请输入数据：\n");
    for(int i=0;;i++)  //
    {
        scanf("%d",&e);
        if(Q->size==0)  //当插入第一个元素时
        {
            Q->front->date=e;  
            Q->rear=Q->front;  //头尾指针都指向第一个结点
            Q->size++;
        }
        else  
        {
            p=(QueuePtr)malloc(sizeof(QNode));
            if(!p)
              exit(0);
            p->date=e;  
            Q->rear->next=p;
            Q->rear=p;
            Q->rear->next=NULL;
            Q->size++; 
        }
        if(getchar()=='\n')
            break;
    }
}
//打印队列元素
void ShowQueue(LinkQueue *Q)
{
    printf("队列内的元素为：\n");
    int e;
    QNode *p;
    p=Q->front;
    for(int i=0;i<Q->size;i++)
    {
        e=p->date;
        printf("%d ",e);
        p=p->next;
    }
    printf("\n");
}

int main()
{
    LinkQueue Q,*p;
    p=&Q;
    Push_Queue(p);
    ShowQueue(p);
    InsertQueue(p, 7);
    ShowQueue(p);
    Pop_Queue(p);
    ShowQueue(p);
}
/* 运行结果
请输入数据：
1 2 3 4 5 6
队列内的元素为：
1 2 3 4 5 6 
队列内的元素为：
1 2 3 4 5 6 7 
队列内的元素为：
2 3 4 5 6 7 
Program ended with exit code: 0
*/

Queue sequentially storing the circular queue structure ---

Why implement a circular queue ( images from the data structure Yan Wei Min ):

The figure is an ordinary sequential store queue, the queue after the data is stored, each of a deleted element, the pointer will move the front, a point on the front space will be wasted, thereby introducing circular queue;

The principle of the cycle queue:

The figure shows the circular queue; seen from the pictures, when the front REAR equal, the queue may be empty or full, the solution there are two ways, one is a defined integer number of elements in the data record; other It would be to sacrifice a storage space when the (rear + 1)% MIXSIEZ == front is full; the second method discussed below;

Implementation process:

• When the insertion and deletion, the pointer are moved clockwise in the circular list;
• When an element is inserted, rear = (rear + 1)% MIXSIZE, i.e. a backward movement;
• Deleting an element, front = (front + 1)% MIXSIZE, i.e. a backward movement;
• Analyzing the queue is full: (rear + 1)% MIXSIEZ == front

Explanation: The reason why the (rear + 1)% MIXSIEZ == front instead of (rear + 1) == front to determine whether the queue is full, because the queue after making a series of insert and delete operations may be less than front rear , as shown above, then back to 0 after 5, modulo method can solve this problem, front = (front + 1)% MIXSIZE and rear = (rear + 1)% MIXSIZE is the same reason;

Code:

#include<stdio.h>
#include <stdlib.h>
#include<malloc.h>
#define MIXSIZE 100   //最大存储空间

typedef struct QNode
{
    int size;  
    int front;
    int rear;
    int *base;
    
}QNode;

//初始化
void InitQueue(QNode *Q)
{
    Q->base=(int *)malloc(MIXSIZE*sizeof(int));
    Q->front=Q->rear=0;
    Q->size=MIXSIZE;
}
//插入
void InsertQueue(QNode *Q,int e)
{
   if((Q->rear+1)%MIXSIZE==Q->front)
        printf("队列已满\n");
    Q->base[Q->rear]=e;
    Q->rear=(Q->rear+1)%MIXSIZE;
}
//删除
void Pop_Queue(QNode *Q)
{
    int e;
    e=Q->base[Q->front++];
}
//输入元素
void Push_Queue(QNode *Q)
{
    int e;
    printf("请输入元素：\n");
    for(int i=0;;i++)
    {
        scanf("%d",&e);
        Q->base[Q->rear]=e;
        Q->rear=(Q->rear+1)%MIXSIZE;
        if(getchar()=='\n')  //按回车键结束输入
            break;
    }
    
}
//打印所以元素
void ShowQueue(QNode *Q)
{
    int e;
    int t=Q->front;
    while(t!=Q->rear)
    {
        e=Q->base[t];
        printf("%d ",e);
        t=(t+1)%MIXSIZE;
    }
    printf("\n");
}

int main()
{
    QNode Q,*p;
    p=&Q;
    InitQueue(p);
    Push_Queue(p);
    ShowQueue(p);
    InsertQueue(p,8);
    ShowQueue(p);
    Pop_Queue(p);
    ShowQueue(p);
}
/* 运行结果
请输入元素：
1 2 3 4 5
1 2 3 4 5 
1 2 3 4 5 8 
2 3 4 5 8 
Program ended with exit code: 0
*/