MAKEMAZE - VALIDATE THE MAZE


There are many algorithms to generate maze. (http://en.wikipedia.org/wiki/Maze_generation_algorithm). After generating the maze we’ve to validate whether it’s a valid maze or not. A valid maze has exactly one entry point and exactly one exit point (exactly 2 openings in the edges) and there must be at least one path from the entry point to exit point.

Given a maze, just find whether the maze is "valid" or "invalid".

Input

The first line consists of an integer t, the number of test cases. Then for each test case, the first line consists of two integers m and n, the number of rows and columns in the maze. Then contains the description of the matrix M of order mxn. M[i][j]=# represents a wall and M[i][j]='.' represents a space.

Output

For each test case find whether the maze is "valid" or "invalid".

Constraints

1<=t<=10000

1<=m<=20

1<=n<=20

Example

Input:
6
4 4
####
#...
#.##
#.##
5 5
#.###
#..##
##..#
#.#.#
###.#
1 1
.
5 1
#
#
.
.
#
2 2
#.
.#
3 4
#..#
#.##
#.##

Output:
valid
valid
invalid
valid
invalid
invalid

hide comments
Mitch Schwartz: 2014-07-10 17:17:20

@sudharshan G: your brain.

sudharshan G: 2014-07-10 17:01:07

where i get this code please help

|RAMSDEN|: 2014-06-27 09:27:46

many WAs due to silly mistake
:p wasn't clearing queue at every iteration..
input format is same as mentioned:)

Master_Mind: 2014-06-14 09:02:12

plzz provide some tricky cases.
any reasons for wa.

Vipul Pandey: 2014-02-04 21:53:35

take input character by character using cin or getchar as there are spaces in the input. costed me WA.

Last edit: 2014-02-04 21:54:02
Rishav Goyal: 2014-02-03 12:35:30

Awesome fun at WA ;)

P_Quantum: 2014-01-19 07:04:47

easy one..!!

The Joker: 2013-12-12 23:21:48

can someone give some tricky test cases plz...
getting WA dont knw why... :(
submission id 10092196

BLANKRK: 2013-12-12 23:21:48

enjoyed solving this.... :)

sobhan: 2013-12-12 23:21:48

plz give me input :)


Added by:cegprakash
Date:2012-05-11
Time limit:1s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: ASM64 GOSU