LABYR1 - Labyrinth

The northern part of the Pyramid contains a very large and complicated labyrinth. The labyrinth is divided into square blocks, each of them either filled by rock, or free. There is also a little hook on the floor in the center of every free block. The ACM have found that two of the hooks must be connected by a rope that runs through the hooks in every block on the path between the connected ones. When the rope is fastened, a secret door opens. The problem is that we do not know which hooks to connect. That means also that the neccessary length of the rope is unknown. Your task is to determine the maximum length of the rope we could need for a given labyrinth.


The input consists of T test cases. The number of them (T) is given on the first line of the input file. Each test case begins with a line containing two integers C and R (3 <= C,R <= 1000) indicating the number of columns and rows. Then exactly R lines follow, each containing C characters. These characters specify the labyrinth. Each of them is either a hash mark (#) or a period (.). Hash marks represent rocks, periods are free blocks. It is possible to walk between neighbouring blocks only, where neighbouring blocks are blocks sharing a common side. We cannot walk diagonally and we cannot step out of the labyrinth.

The labyrinth is designed in such a way that there is exactly one path between any two free blocks. Consequently, if we find the proper hooks to connect, it is easy to find the right path connecting them.


Your program must print exactly one line of output for each test case. The line must contain the sentence "Maximum rope length is X." where Xis the length of the longest path between any two free blocks, measured in blocks.


Sample Input:
3 3
7 6

Sample output:
Maximum rope length is 0.
Maximum rope length is 8.
Warning: large Input/Output data, be careful with certain languages

hide comments
joe85123: 2018-11-04 17:29:49

pretty much the same solution with "the longest path in a tree"
can be done using only one dfs!

markomafko972: 2018-07-19 17:44:28

Try CLCKBAIT after this!

hello_world123: 2018-06-13 16:22:03

Can be done using only DFS ..... But requires more thinking

ultra_7: 2018-01-02 09:31:03

input is C first and then R. dont miss this.

aniket000: 2017-12-30 06:37:23

took me 3 hours to debug but AC finally!! :)

Omar: 2017-10-16 01:43:29

make sure to read rows and column in the right way .

rohit1507: 2017-09-12 07:56:00

Please take care of the corner case. "There is exactly one path between any two free block". Cost me 1 WA.

hk_visact: 2017-08-24 11:48:43

Faced NZEC runtime error due to limited stack space of java.
Refer to this link to increase stack space

finally AC :)

the_phoenixx: 2017-06-28 10:40:19

Easy One !!
just using Dfs but good one for begineers

tech123: 2017-05-23 21:29:21

Be careful about the output format..And especially the fullstop at the end of output...

Added by:adrian
Time limit:5s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Resource:ACM Central European Programming Contest, Prague 1999