UVA - 540：Team Queue

Team Queue

来源：UVA

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参考资料：《算法竞赛入门经典》P117

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题目

Queues and Priority Queues are data structures which are known to most computer scientists. The Team Queue, however, is not so well known, though it occurs often in everyday life. At lunch time the queue in front of the Mensa is a team queue, for example. In a team queue each element belongs to a team. If an element enters the queue, it first searches the queue from head to tail to check if some of its teammates (elements of the same team) are already in the queue. If yes, it enters the queue right behind them. If not, it enters the queue at the tail and becomes the new last element (bad luck). Dequeuing is done like in normal queues: elements are processed from head to tail in the order they appear in the team queue. Your task is to write a program that simulates such a team queue.

输入

The input file will contain one or more test cases. Each test case begins with the number of teams t (1 ≤ t ≤ 1000). Then t team descriptions follow, each one consisting of the number of elements belonging to the team and the elements themselves. Elements are integers in the range 0…999999. A team may consist of up to 1000 elements.
Finally, a list of commands follows. There are three different kinds of commands:
• ENQUEUE x — enter element x into the team queue
• DEQUEUE — process the first element and remove it from the queue
• STOP — end of test case
The input will be terminated by a value of 0 for t.
Warning: A test case may contain up to 200000 (two hundred thousand) commands, so the implementation of the team queue should be efficient: both enqueing and dequeuing of an element should only take constant time.

输出

For each test case, first print a line saying ‘Scenario #k’, where k is the number of the test case. Then, for each ‘DEQUEUE’ command, print the element which is dequeued on a single line. Print a blank line after each test case, even after the last one.

输入样例

2
3 101 102 103
3 201 202 203
ENQUEUE 101
ENQUEUE 201
ENQUEUE 102
ENQUEUE 202
ENQUEUE 103
ENQUEUE 203
DEQUEUE
DEQUEUE
DEQUEUE
DEQUEUE
DEQUEUE
DEQUEUE
STOP
2
5 259001 259002 259003 259004 259005
6 260001 260002 260003 260004 260005 260006
ENQUEUE 259001
ENQUEUE 260001
ENQUEUE 259002
ENQUEUE 259003
ENQUEUE 259004
ENQUEUE 259005
DEQUEUE
DEQUEUE
ENQUEUE 260002
ENQUEUE 260003
DEQUEUE
DEQUEUE
DEQUEUE
DEQUEUE
STOP
0

输出样例

Scenario #1
101
102
103
201
202
203
Scenario #2
259001
259002
259003
259004
259005
260001

解题思路

设置两个队列，队列q放置团队编号，队列q2[t]放置团队t中队员编号。结合代码理解。

参考代码

#include
#include
#include
#define MAXN 1005
using namespace std;
int main(){
	int t,kase=0;
	while(scanf("%d",&t)==1 && t)	{
		printf("Scenario #%d\n",++kase);
		map<int,int> team;
		for(int i=0;i<t;i++){
			int n,x;
			scanf("%d",&n);
			while(n--){scanf("%d",&x);team[x]=i;}
		}
		
		queue<int> q,q2[MAXN];
		while(true){
			int x;
			char cmd[10];
			scanf("%s",cmd);
			if(cmd[0]=='S')break;
			else if(cmd[0]=='D'){
				int t=q.front();
				printf("%d\n",q2[t].front());q2[t].pop();
				if(q2[t].empty())q.pop();
			}
			else if(cmd[0]=='E'){
				scanf("%d",&x);
				int t=team[x];
				if(q2[t].empty())q.push(t);
				q2[t].push(x);
			}
		}
		printf("\n");
	}
	return 0;
}