acm 1083

Posted on 2007-06-03 21:03  少林  阅读(...)  评论(...编辑  收藏

Moving Tables
Time Limit:1000MS  Memory Limit:10000K
Total Submit:2352 Accepted:880

Description
The famous ACM (Advanced Computer Maker) Company has rented a floor of a building whose shape is in the following figure.


The floor has 200 rooms each on the north side and south side along the corridor. Recently the Company made a plan to reform its system. The reform includes moving a lot of tables between rooms. Because the corridor is narrow and all the tables are big, only one table can pass through the corridor. Some plan is needed to make the moving efficient. The manager figured out the following plan: Moving a table from a room to another room can be done within 10 minutes. When moving a table from room i to room j, the part of the corridor between the front of room i and the front of room j is used. So, during each 10 minutes, several moving between two rooms not sharing the same part of the corridor will be done simultaneously. To make it clear the manager illustrated the possible cases and impossible cases of simultaneous moving.

For each room, at most one table will be either moved in or moved out. Now, the manager seeks out a method to minimize the time to move all the tables. Your job is to write a program to solve the manager's problem.

 

Input
The input consists of T test cases. The number of test cases ) (T is given in the first line of the input file. Each test case begins with a line containing an integer N , 1 <= N <= 200, that represents the number of tables to move.
Each of the following N lines contains two positive integers s and t, representing that a table is to move from room number s to room number t each room number appears at most once in the N lines). From the 3 + N -rd
line, the remaining test cases are listed in the same manner as above.

Output
The output should contain the minimum time in minutes to complete the moving, one per line.

Sample Input

3
4
10 20
30 40
50 60
70 80
2
1 3
2 200
3
10 100
20 80
30 50

 

Sample Output

10
20
30
      
       今天做了pku上的1083题,一看题目.觉的很难,不知道怎样使用动态规划..也不知道找最优子结构.硬着皮头想了几遍,没有任何进展.只好求助于discuss了.其中一个思路,真的太秒了:首先把各个走廊从1到200进行编号.编号后,每当移动一个桌子,则记录该次移动过程所占用的走廊段的使用次数加一.最后,求出所有走廊段中使用次数最大的再乘以10,就是最小的移动的时间了.
         这思路简直太奇妙了,想想也是.在现实生活中,也是这样啊.所以一定要活学活用.动态规划虽说难度较大,但只要我们多动脑,多联系实际.往往一些巧妙的思路,就形成了.

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