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Do the math solution in Clear category for Pearls in the Box by nickie
def checkio(pearls, N): # explained in the comment and in Veky's solution
P = len(pearls)
C = sum(1 for p in pearls if p == "w")
r = (1 - (1-2*C/P) * (1-2/P)**(N-1)) / 2
return round(r, 2)
#These "asserts" using only for self-checking and not necessary for auto-testing
if __name__ == '__main__':
assert checkio('bbw', 3) == 0.48, "1st example"
assert checkio('wwb', 3) == 0.52, "2nd example"
assert checkio('www', 3) == 0.56, "3rd example"
assert checkio('bbbb', 1) == 0, "4th example"
assert checkio('wwbb', 4) == 0.5, "5th example"
assert checkio('bwbwbwb', 5) == 0.48, "6th example"
Feb. 6, 2014
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