EDIT: This was a while ago and I've since got it working, if you'd like to see the code it's included at github.com/LewisGaul/minegaulerQt.
I'm trying to write a program to calculate probabilities for the game minesweeper, and have had some difficulty working out how best to structure it. While it may seem quite simple at first with the example below, I would like to know the best way to allow for more complex configurations. Note I am not looking for help with how to calculate probabilities - I know the method, I just need to implement it!
To make it clear what I'm trying to calculate, I will work through a simple example which can be done by hand. Consider a minesweeper configuration
# # # #
# 1 2 #
# # # #
where # represents an unclicked cell. The 1 tells us there is exactly 1 mine in the leftmost 7 unclicked cells, the 2 tells us there are exactly 2 in the rightmost 7. To calculate the probability of each individual cell containing a mine, we need to determine all the different cases (only 2 in this simple case):
1 mine in leftmost 3 cells, 2 mines in rightmost 3 cells (total of 3 mines, 3x3=9 combinations).
1 mine in center 4 cells, 1 mine in rightmost 3 cells (total of 2 mines, 4x3=12 combinations).
Given the probability of a mine being in a random cell is about 0.2, it is (in a random selection of cells) about 4 times more likely there is a total of 2 mines rather than a total of 3, so the total number of mines in a configuration matters, as well as the number of combinations of each configuration. So in this case the probability of case 1 is 9/(9+4x12)=0.158, and the probability of there being a mine in a given leftmost cell is therefore about 0.158/3=0.05, as those cells are effectively equivalent (they share exactly the same revealed neighbours).
I have created a GUI with Tkinter which allows me to easily enter configurations such as the one in the example, which stores the grid as a numpy array. I then made a NumberGroup class which isolates each of the clicked/numbered cells, storing the number and a set of the coordinates of its unclicked neighbours. These can be subtracted to get equivalence groups... Although this would not be as straightforward if there were three or more numbers instead of just two. But I am unsure how to go from here to getting the different configurations. I toyed with making a Configuration class, but am not hugely familiar with how different classes should work together. See working code below (numpy required).
Note: I am aware I could have attempted to use a brute force approach, but if possible I would like to avoid that, keeping the equivalent groups separate (in the above example there are 3 equivalence groups, the leftmost 3, the middle 4, the rightmost 3). I would like to hear your thoughts on this.
import numpy as np
grid = np.array(
[[0, 0, 0, 0],
[0, 2, 1, 0],
[0, 0, 0, 0]]
)
dims = (3, 4) #Dimensions of the grid
class NumberGroup(object):
def __init__(self, mines, coords, dims=None):
"""Takes a number of mines, and a set of coordinates."""
if dims:
self.dims = dims
self.mines = mines
self.coords = coords
def __repr__(self):
return "<Group of {} cells with {} mines>".format(
len(self.coords), self.mines)
def __str__(self):
if hasattr(self, 'dims'):
dims = self.dims
else:
dims = (max([c[0] for c in self.coords]) + 1,
max([c[1] for c in self.coords]) + 1)
grid = np.zeros(dims, int)
for coord in self.coords:
grid[coord] = 1
return str(grid).replace('0', '.').replace('1', '#')
def __sub__(self, other):
if type(other) is NumberGroup:
return self.coords - other.coords
elif type(other) is set:
return self.coords - other.coords
else:
raise TypeError("Can only subtract a group or a set from another.")
def get_neighbours(coord, dims):
x, y = coord
row = [u for u in range(x-1, x+2) if u in range(dims[0])]
col = [v for v in range(y-1, y+2) if v in range(dims[1])]
return {(u, v) for u in row for v in col}
groups = []
all_coords = [(i, j) for i in range(dims[0])
for j in range(dims[1])]
for coord, nr in [(c, grid[c]) for c in all_coords if grid[c] > 0]:
empty_neighbours = {c for c in get_neighbours(coord, dims)
if grid[c] == 0}
if nr > len(empty_neighbours):
print "Error: number {} in cell {} is too high.".format(nr, coord)
break
groups.append(NumberGroup(nr, empty_neighbours, dims))
print groups
for g in groups:
print g
print groups[0] - groups[1]
UPDATE:
I have added a couple of other classes and restructured a bit (see below for working code), and it is now capable of creating and displaying the equivalence groups, which is a step in the right direction. However I still need to work out how to iterate through all the possible mine-configurations, by assigning a number of mines to each group in a way that creates a valid configuration. Any help is appreciated.
For example,
# # # #
# 2 1 #
# # # #
There are three equivalence groups G1: the left 3, G2: the middle 4, G3: the right 3. I want the code to loop through, assigning groups with mines in the following way:
- G1=2 (max the first group) => G2=0 => G3=1 (this is all configs with G1=2)
- G1=1 (decrease by one) => G2=1 => G3=0 (this is all with G1=1)
- G1=0 => G2=2 INVALID
So we arrive at both configurations. This needs to work for more complicated setups!
import numpy as np
def get_neighbours(coord, dims):
x, y = coord
row = [u for u in range(x-1, x+2) if u in range(dims[0])]
col = [v for v in range(y-1, y+2) if v in range(dims[1])]
return {(u, v) for u in row for v in col}
class NrConfig(object):
def __init__(self, grid):
self.grid = grid
self.dims = grid.shape # Dimensions of grid
self.all_coords = [(i, j) for i in range(self.dims[0])
for j in range(self.dims[1])]
self.numbers = dict()
self.groups = []
self.configs = []
self.get_numbers()
self.get_groups()
self.get_configs()
def __str__(self):
return str(self.grid).replace('0', '.')
def get_numbers(self):
for coord, nr in [(c, self.grid[c]) for c in self.all_coords
if self.grid[c] > 0]:
empty_neighbours = {c for c in get_neighbours(
coord, self.dims) if self.grid[c] == 0}
if nr > len(empty_neighbours):
print "Error: number {} in cell {} is too high.".format(
nr, coord)
return
self.numbers[coord] = Number(nr, coord, empty_neighbours,
self.dims)
def get_groups(self):
coord_neighbours = dict()
for coord in [c for c in self.all_coords if self.grid[c] == 0]:
# Must be a set so that order doesn't matter!
coord_neighbours[coord] = {self.numbers[c] for c in
get_neighbours(coord, self.dims) if c in self.numbers}
while coord_neighbours:
coord, neighbours = coord_neighbours.popitem()
equiv_coords = [coord] + [c for c, ns in coord_neighbours.items()
if ns == neighbours]
for c in equiv_coords:
if c in coord_neighbours:
del(coord_neighbours[c])
self.groups.append(EquivGroup(equiv_coords, neighbours, self.dims))
def get_configs(self):
pass # WHAT GOES HERE?!
class Number(object):
"""Contains information about the group of cells around a number."""
def __init__(self, nr, coord, neighbours, dims):
"""Takes a number of mines, and a set of coordinates."""
self.nr = nr
self.coord = coord
# A list of the available neighbouring cells' coords.
self.neighbours = neighbours
self.dims = dims
def __repr__(self):
return "<Number {} with {} empty neighbours>".format(
int(self), len(self.neighbours))
def __str__(self):
grid = np.zeros(self.dims, int)
grid[self.coord] = int(self)
for coord in self.neighbours:
grid[coord] = 9
return str(grid).replace('0', '.').replace('9', '#')
def __int__(self):
return self.nr
class EquivGroup(object):
"""A group of cells which are effectively equivalent."""
def __init__(self, coords, nrs, dims):
self.coords = coords
# A list of the neighbouring Number objects.
self.nr_neighbours = nrs
self.dims = dims
if self.nr_neighbours:
self.max_mines = min(len(self.coords),
max(map(int, self.nr_neighbours)))
else:
self.max_mines = len(coords)
def __repr__(self):
return "<Equivalence group containing {} cells>".format(
len(self.coords))
def __str__(self):
grid = np.zeros(self.dims, int)
for coord in self.coords:
grid[coord] = 9
for number in self.nr_neighbours:
grid[number.coord] = int(number)
return str(grid).replace('0', '.').replace('9', '#')
grid = np.array(
[[0, 0, 0, 0],
[0, 2, 1, 0],
[0, 0, 0, 0]]
)
config = NrConfig(grid)
print config
print "Number groups:"
for n in config.numbers.values():
print n
print "Equivalence groups:"
for g in config.groups:
print g