Windows Message Queue

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 9041    Accepted Submission(s): 3746

 

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!

STL里面的优先队列默认对象是int,并且使用vector存储数据，当需要使用结构体构建队列元素的时候，我们就要重载C++里面的operator<操作符，重载使用的是bool friend operator < (edge a, edge b)这个友函数，具体操作请看注释

AC代码

#include<cstdlib>
#include<queue>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
struct edge
{
    int pr;//存储优先级 
    int num;//存储指令输入的顺序 
    int digit;
    char name[500];
    bool friend operator < (edge a, edge b)//返回true时b优先级高于a 
    {
        if(a.pr == b.pr) 
        {
            return a.num > b.num;//优先级相等时使用FIFO判断哪一条指令先出去 
        }
        return a.pr > b.pr;//优先级数字越大代表的优先级反而小 
    }
};
int main(void)
{
    priority_queue<edge> que;
    char s[10];
    int k = 1;
    while(scanf("%s", s) != EOF)
    {
        if(strcmp(s, "GET") == 0)
        {
            if(que.empty())
            {
                printf("EMPTY QUEUE!\n");
            }
            else
            {
                printf("%s %d\n", que.top().name, que.top().digit);
                que.pop();
            }
        }
        if(strcmp(s, "PUT") == 0)
        {
            edge t;
            scanf("%s %d %d", t.name, &t.digit, &t.pr);
            t.num = k;
            que.push(t);
            k++;
        }
    }
    return 0;
}