The birthday problem

birthday_problem.py

# birthday problem - http://en.wikipedia.org/wiki/Birthday_problem

def get_prob(n):
  p, i = 1.0, 0
    while (i < n):
		p = p * (365 - i) / 365
		i += 1
	return (1 - p)
 
def func_get_prob(n):
	""" functional version of the above function """
	def iter(n):
		if (n == 0):
			return 1
		else:
			return (365.0 - n) / 365 * iter(n-1)
	return 1 - iter(n-1)
 
def solve_birthday_problem(n, f):
	print "P(n={:}) = {:.2%}".format(n, f(n))
 
solve_birthday_problem(23, get_prob) # output: 50.73%
solve_birthday_problem(23, func_get_prob) # output: 50.73%