链表仿真队列

我们可以使用链表的方式仿真队列，参考程序如下。

//链表仿真队列
#include<iostream>
#include<stdlib.h>

using namespace std;
typedef struct QueueNode node;
typedef struct QueueNode *link;
struct QueueNode
{
    int data;
    struct QueueNode *next;
};

link front = NULL;//队头
link rear= NULL;  //队尾

void addqueue(int value)
{
    link new_node;
    new_node=(link)malloc(sizeof(node));
    new_node->data=value;
    new_node->next=NULL;
    if(front==NULL)  //若为链表第一个元素
        front=new_node;
    else
        rear->next=new_node;
    rear=new_node;
}

int delqueue()
{
    link top;
    int temp;
    if(front !=NULL)
    {
        top=front;
        front =front ->next;
        temp=top->data;
        free(top);
        return temp;
    }
    else
    {
        rear=NULL;
        return -1;
    }
}

void display()
{
    link point ;
    point =front;
    while(point!=NULL)
    {
        cout<<point->data<<' ';
        point=point->next;
    }
    cout<<endl;
}

int main()
{
    int select;
    int i,temp;
    while(1)
    {
        cout<<"1.Input a data\n";
        cout<<"2.Output a data\n";
        cout<<"3.Exit\n";
        cin>>select;
        switch(select)
        {
        case 1:
            cout<<"Please input a value "<<endl;
            cin>>temp;
            addqueue(temp);
            break;
        case 2:
            if(delqueue()==-1)  //如果队列是空
                cout<<"The queue is empty!"<<temp<<endl;
            else
                cout<<"The out value is "<<temp<<endl;
            break;
        case 3:
            return 0;
        }
        system("cls");          //清空屏幕，此命令只能在Windows平台下使用
        display();
    }
    return 0;
}