ZOJ 2724 Windows Message Queue（二叉堆or优先队列）

Windows Message Queue
Time Limit:2000MS     Memory
Limit:65536KB     64bit
IO Format:%lld & %llu
[b]Description[/b]

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.


[b]Input
[/b]

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.


[b]Output
[/b]

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.


[b]Sample
Input[/b]

GETPUT msg1 10 5PUT msg2 10 4GETGET
GET

[b]Sample Output
[/b]

EMPTY QUEUE!
msg2 10
msg1 10
EMPTY QUEUE!

这是一道典型的优先队列问题，队列
a44a
中储存待处理的消息，按照优先级值递增顺序存放，若优先级相同，则先来者前，后来者后。
一：二叉堆

#include <iostream>
#include <stdio.h>
#include <string.h>
using namespace std;

const int maxn=60005;
int top,used;
int heap[maxn];

struct M
{
char name[100];
int num;
int pri;
int t;
}msg[maxn];

int comp(int a,int b)
{
if(msg[a].pri<msg[b].pri)
return -1;
if(msg[a].pri>msg[b].pri)
return 1;
if(msg[a].t<msg[b].t)
return -1;
if(msg[a].t>msg[b].t)
return 1;
return 0;
}

int main()
{
char s[100];
top=0;
used=0;
int cn=0;
while(scanf("%s",s)!=EOF)
{
if(strcmp(s,"GET")==0)
{
if(!top) printf("EMPTY QUEUE!\n");
else
{
printf("%s %d\n",msg[heap[1]].name,msg[heap[1]].num);
int k=1;
heap[k]=heap[top--];
while(k*2<=top)
{
int t=k*2;
if(t<top&&comp(heap[t+1],heap[t])<0)
t++;
if(comp(heap[t],heap[k])<0)
{
swap(heap[t],heap[k]);
k=t;
}
else break;
}
}
}
else
{
scanf("%s%d%d",msg[used].name,&msg[used].num,&msg[used].pri);
msg[used].t=cn++;
int k=++top;
heap[k]=used++;
while(k>1)
{
int t=k/2;
if(comp(heap[t],heap[k])>0)
{
swap(heap[t],heap[k]);
k=t;
}
else break;
}
}
}
return 0;
}

二：用优先队列 priority_queue

因为优先队列默认排序是由大到小的，因此自定义优先级。

#include <iostream>
#include <stdio.h>
#include <algorithm>
#include <queue>
#include <string.h>
using namespace std;

struct node
{
friend bool operator<(node a,node b)
{
return a.t>b.t;
}
char name[50];
int num;
int t;
};

int main()
{
priority_queue<node> Q;
char c[50];
node n;
while(scanf("%s",c)!=EOF)
{
if(strcmp(c,"GET")==0)
{
if(Q.empty())
printf("EMPTY QUEUE!\n");
else
{
printf("%s %d\n",Q.top().name,Q.top().num);
Q.pop();
}
}
else
{
scanf("%s %d %d",n.name,&n.num,&n.t);
Q.push(n);
}
}
return 0;
}