Windows Message Queue(priority_queue优先队列）

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本文介绍了一个关于消息队列的模拟实现，重点在于处理不同优先级的消息及FIFO原则。通过优先级队列的应用，实现了消息的高效管理和处理。

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Windows Message Queue

Time Limit : 2000/1000ms (Java/Other) Memory Limit : 65536/32768K (Java/Other)

Total Submission(s) : 17 Accepted Submission(s) : 8

Problem Description

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!

Author

ZHOU, Ran

Source

Zhejiang University Local Contest 2006, Preliminary

题意：PUT表示输入，GET表示输出，输入时包括“信息名参数优先级”其中优先级越小则优先程度越高，当优先级相同时则输出最早输入的那个

若队列为空则输出EMPTY QUEUE!不为空输出优先级（且最早输入的值）“信息名参数值”

题解：priority_queue的应用，此题要写一个比较方式不仅要按优先级排序还要按输入先后顺序排序，每次输出即为队首值

#include<cstdio>
#include<queue>
using namespace std;
const int M=100;
struct node
{
    char str[100];
    int m,n,i;
    friend bool operator<(const node &a,const node &b)
    {
        if(a.n==b.n)
         return a.i>b.i;
        return a.n>b.n;
    }
}tmp;
int main()
{
    char s1[5];
    int k=0;
    priority_queue<node>Q;
    while(scanf("%s",s1)!=EOF)
    {
        if(s1[0]=='G')
        {
            if(!Q.empty())
            {
                tmp=Q.top();
                Q.pop();
                printf("%s %d\n",tmp.str,tmp.m);
            }
            else
             printf("EMPTY QUEUE!\n");

        }
        else
        {
            scanf("%s%d%d",tmp.str,&tmp.m,&tmp.n);
            tmp.i=k++;
            Q.push(tmp);
        }
    }
    return 0;
}