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pmallory/stairs.py

Last active March 1, 2017 01:29
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Stairs problem: dynamic programming solution
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stairs.py
from decimal import *
def count_ways(n, max_step_size=2):
table = [Decimal(1), Decimal(1), Decimal(2)]
assert len(table) >= max_step_size
for i in xrange(3,n+1):
table.append(sum(table[i-max_step_size:i]))
return table[n]
def probability(n):
return count_ways(n, 2) / count_ways(n, 3)
print probability(2000)
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