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

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

hide comments
2014-07-10 17:17:20 Mitch Schwartz
@sudharshan G: your brain.
2014-07-10 17:01:07 sudharshan G
where i get this code please help
2014-06-27 09:27:46 |RAMSDEN|
many WAs due to silly mistake
:p wasn't clearing queue at every iteration..
input format is same as mentioned:)
2014-06-14 09:02:12 Master_Mind
plzz provide some tricky cases.
any reasons for wa.
2014-02-04 21:53:35 Vipul Pandey
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
2014-02-03 12:35:30 Rishav Goyal
Awesome fun at WA ;)
2014-01-19 07:04:47 P_Quantum
easy one..!!
2013-12-12 23:21:48 The Joker
can someone give some tricky test cases plz...
getting WA dont knw why... :(
submission id 10092196
2013-12-12 23:21:48 BLANKRK
enjoyed solving this.... :)
2013-12-12 23:21:48 sobhan
plz give me input :)
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