Windows Message Queue

灰太狼 2022-04-03 09:56 180阅读 0赞

### 题目描述： ###

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!

##### 分析： #####

本题， 如果用Ｃ语言来写的话，是比较繁琐的。并且容易出错，不过如果我们用C++里面的容器进行操作的话， 会发现， 其实这个操作时十分简单的。我们只需要使用优先队列就可以了。

#include"stdio.h"
    #include"string.h"
    #include"queue"
     using namespace std;
    typedef struct node
    {
        char name[16];
        int value;
        int priority;
        int dd;、
       //这里是优先队列的最基本排序操作， 也是核心操作。
        bool operator <(const node &a) const
        {   if(priority==a.priority)
                  return dd>a.dd;
            return priority>a.priority;
        }
    } NEWS;
    NEWS news;
    priority_queue <NEWS> q;
    int main()
    {
        long long i,j,k=0;
        char stringA[100];
        NEWS T;
        while(~scanf("%s",stringA))
        {
            if(stringA[0]=='G')
               { if(!q.empty())
                 {T=q.top();q.pop();
                 printf("%s %d\n",T.name,T.value);
                 }
                 else
                    printf("EMPTY QUEUE!\n");
               }
            else
            {
                scanf("%s%d%d",T.name,&T.value,&T.priority);
                T.dd=k++;
                q.push(T);
            }
    
        }
    }