ZOJ Problem Set - 2724 Windows Message Queue

Windows Message Queue

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Time Limit: 2 Seconds      Memory Limit: 65536 KB

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Message queue is the basic fundamental of windows system. For each process, the system maintains a message queue. If something happens to this process, such as mouse click, text change, the system will add a message to the queue. Meanwhile, the process will do a loop for getting message from the queue according to the priority value if it is not empty. Note that the less priority value means the higher priority. In this problem, you are asked to simulate the message queue for putting messages to and getting message from the message queue.

Input

There's only one test case in the input. Each line is a command, "GET" or "PUT", which means getting message or putting message. If the command is "PUT", there're one string means the message name and two integer means the parameter and priority followed by. There will be at most 60000 command. Note that one message can appear twice or more and if two messages have the same priority, the one comes first will be processed first.(i.e., FIFO for the same priority.) Process to the end-of-file.

Output

For each "GET" command, output the command getting from the message queue with the name and parameter in one line. If there's no message in the queue, output "EMPTY QUEUE!". There's no output for "PUT" command.

Sample Input

GET
PUT msg1 10 5
PUT msg2 10 4
GET
GET
GET

Sample Output

EMPTY QUEUE!
msg2 10
msg1 10
EMPTY QUEUE!

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Author: ZHOU, Ran

Source: Zhejiang University Local Contest 2006, Preliminary 

分析：

题意：

维护一个优先队列（元素要求从小到大排序，与pq的默认顺序相反），给两个操作，一个是入队操作PUT，后面跟着入队的元素；另一个是出队操作。

输出出队结果。

需要注意的是：由于本题的输入输出量较大（最大可能达到6万，而且输入输出有字符串），只能选择用scanf和printf，否则超时。

ac代码：

//本题的输入输出量较大（最大可能达到6万，而且输入输出有字符串），只能选择用scanf和printf，否则超时
#include <iostream>
#include<cstdio>
#include<cstring>
#include<queue>
#include<algorithm>
using namespace std;
const int maxn=100;
const int maxm=60000+10;
struct Message
{
    char name[maxn];
    int num;
    int priority;
    bool operator <(const Message &m) const
    {
        return m.priority<priority;
    }
}message;//作为临时输入的变量，放进pq队列就可以，所以这里不用维护一个数组
priority_queue<Message> pq;
int main()
{
    char c[maxn];
    while(scanf("%s",c)!=EOF)
    {
        if(strcmp(c,"PUT")==0)
        {
            scanf("%s%d%d",&message.name,&message.num,&message.priority);
            pq.push(message);
        }
        else
        {
            if(pq.empty())
            {
                printf("EMPTY QUEUE!\n");
            }
            else
            {
                printf("%s %d\n",pq.top().name,pq.top().num);
                pq.pop();
            }
        }
    }
    return 0;
}