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Calculate the frequencies of different total face values for rolling n six sided dice.
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#Naive version. Takes a couple of minutes for 11 dice on my laptop | |
#from itertools import product | |
#from collections import Counter | |
# | |
#dice = int(input('How many dice? ')) | |
#result = Counter(map(sum, product(range(1, 7), repeat=dice))) | |
#print(result) | |
def choose(n, k): | |
""" | |
A fast way to calculate binomial coefficients by Andrew Dalke (contrib). | |
http://stackoverflow.com/a/3025547/500584 | |
""" | |
if 0 <= k <= n: | |
ntok = 1 | |
ktok = 1 | |
for t in range(1, min(k, n - k) + 1): | |
ntok *= n | |
ktok *= t | |
n -= 1 | |
return ntok // ktok | |
else: | |
return 0 | |
def freq(sides, dice, amount): | |
# http://digitalscholarship.unlv.edu/cgi/viewcontent.cgi?article=2852&context=thesesdissertations | |
m = sides | |
n = dice | |
k = amount - dice | |
total = 0 | |
for j in range(max(m, k)): | |
term = (-1) ** j | |
term *= choose(n, j) | |
term *= choose(n - 1 + k - m * j, n - 1) | |
total += term | |
return total | |
sides = 6 | |
dice = int(input('How many dice? ')) | |
sums = range(dice, dice * sides + 1) | |
#freqs = [freq(sides, dice, amount) for amount in sums] | |
freqs = [freq(sides, dice, amount) for amount in sums[:(len(sums) + 1) // 2]] | |
if len(sums) % 2 == 1: | |
freqs += freqs[-2::-1] | |
else: | |
freqs += freqs[-1::-1] | |
result = dict(zip(sums, freqs)) | |
print(result) |
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nice work