From Progteam

Revision as of 21:34, 31 March 2010 by Jinho (Talk | contribs)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to: navigation, search

Problem Number 1138
Sorter: hjfreyer
Source: Unknown

Ships is problem number 1138 on the Peking University ACM site. We've almost solved it!


Probably everyone who ever attended school knows the game where two opposing 
players place a set of ships on a sheet of paper and try to eliminate each 
other's ships by guessing their location. 

In our version of the game, your opponent has distributed the following seven 
ship patterns over a rectangular grid of squares: 

xx  xx    xx  x      x   x
xx   xx  xx   xxx  xxx  xxx  xxxx

Each ship pattern covers exactly four squares. The patterns may be rotated but 
not mirrored. All patterns are guaranteed to be placed completely within the 
boundaries of the rectangle and not to overlap each other, whereas touching 
another pattern or the border is allowed. 

We assume that we are in the middle of the game and that several squares have 
already been uncovered. You will be given a rectangular grid of squares 
representing your current knowledge about the positions of your enemy's ships. 
Every square is marked by one of the following characters: 

'x' if a ship covers the square 
'o' if no ship covers the square 
'.' if the square has not yet been uncovered 

Given that information, you are to decide whether you can determine all 
remaining 'x' squares with at most one miss, i.e. whether you could uncover 
the '.' squares without getting more than one 'o' square before you had all 
'x' squares uncovered. This means you are allowed to hit a 'o' if then the 
solution becomes unique. 


The input file contains several game situations. Every test case starts with a 
line containing two integers h and w. These define width and height of the game 
rectangle, where 2 <= w, h <= 16. 

Each of the next h lines contains a string of w characters. Each of these 
characters is either `x', `o' or `.', depending on the state of the 
corresponding square. 

A blank line separates each game from the next. The input file ends with a 
game having w = 0 and h = 0. This game should not be processed.

For each test case you should first output a line containing the number of the 
game, followed by a line containing either `yes.' (if you can determine all `x' 
with at most one miss) or `no.' (if you cannot determine all `x' without at 
least two misses). 

Output a blank line after every game.

**Sample Input**

10 10

0 0

**Sample Output**

Game #1
Personal tools