双向队列的简单讲解

#include <cstdio>
#include <cstring>
#include <queue>
#include <deque>
#include <algorithm>

using namespace std;
#define MAX 10010
int main()
{
    deque<int>q;  //创建双向队列
    while(!q.empty())//清空双向队列
        q.pop_front();
    int n,a,i,m[MAX]= {0};
    scanf("%d",&n);
    for(i=1; i<=n; i++)
    {
        char s[10];
        scanf(" %s",s);
        if(!strcmp(s,"LIN"))
        {
            scanf("%d",&a);
            q.push_front(a);  //在队列头（左边）存入数据
        }
        else if(!strcmp(s,"RIN"))
        {
            scanf("%d",&a);
            q.push_back(a);//在队列尾（右边）存入数据
        }
        else if(!strcmp(s,"LOUT"))
        {
            if(!q.empty())
                q.pop_front();  //如果队列非空删除队列头（最左边）的数据
            else
                m[i]++;
        }
        else if(!strcmp(s,"ROUT"))
        {
            if(q.empty())
                m[i]++;   
            else
                q.pop_back();
        }
    }
    printf("%d",q.front()); 
    q.pop_front();
    while(!q.empty())
    {
        printf(" %d",q.front());//输出队列中的数据
    q.pop_front();
    }
    printf("\n");
    for(i=1; i<=n; i++)
        if(m[i])
            printf("%d ERROR\n",i);
    return 0;
}