Queue definition and basic operation

1. Definition

1. Queue is a first-in, first-out linear table, and its operation can only be performed on both ends of the table.

2. Classification: chain queue-chain representation; circular queue-sequential representation

Second, the chain queue

Node structure:

typedef struct QNode{
    
    
       int data;
       struct QNode *next;
}QNode,*QPtr;

Chain queue structure

typedef struct {
    
    
       QPtr *front;   //队首指针
       QPtr *rear;    //队尾指针
}LinkQueue;

Create empty queue

Status InitQueue(LinkQueue Q)
{
    
    
  Q.front=Q.rear=(QNode*)malloc(sizeof(QNode));
  if(!Q.front)exit(0); //存储分配失败
  Q.front->next=NULL;
}
  

Enqueue operation

EnQueue(LinkQueue Q,int e)
{
    
    
  QPtr p=(QNode*)malloc(sizeof(QNode));
  if(!p)exit(0);//储存分配失败
 p->next=NULL;
 p->data=e;
 Q.rear->next=p;
 Q.rear=p;
}

Dequeue operation

DeQueue(LinkQueue Q,int e)
{
    
    
  QPtr p=(QNode*)malloc(sizeof(QNode));
  if(!p)exit(0);//储存分配失败
  if(Q.front==Q.rear)return ERROR;//队列为空，无法完成出队操作
  p=Q.front->next;
  e=p->data;
 Q.front->next=p->next;
 if(Q.rear==p)Q>front=Q.rear;
 free(p);
  }

Three, sequential queue-array representation

Enqueue operation

EnQueue(Q[MAX],int x)
{
    
    
   if(rear+1>=MAX)cout<<"队满"<<endl;
   else
   {
    
    
    Q[rear]=x;
    rear++;
   }
}

Dequeue operation

DeQueue(Q[MAX],int e)
{
    
    
 if(front==rear)cout<<"队空"<<endl;
 else
 {
    
    
 e=Q[front];
 front++;
 return e;
 }
}

Four, circular queue

Note: The
conditions for full team are:

(rear+1)%MAX==front

The team empty conditions are:

rear==front