Project Euler Problem/Solutions

projecteuler.py

#!/usr/bin/python

def problem40():
    """
    http://projecteuler.net/problem=40
    An irrational decimal fraction is created by concatenating the positive integers:

    0.123456789101112131415161718192021...

    It can be seen that the 12th digit of the fractional part is 1.

    If dn represents the nth digit of the fractional part, find the value of the following expression.

    d1 x d10 x d100 x d1000 x d10000 x d100000 x d1000000
    """
    global _part; global _int
    _part = ''
    _int = 0

    def dn(digit):
        global _part; global _int
        while(len(_part) <= digit):
            _int += 1
            _part = '{}{}'.format(_part, _int)
        print 'dn({}) is {}'.format(digit, int(_part[digit-1]))
        return int(_part[digit-1])

    assert dn(2) == 2, '{} != 2'.format(dn(2))
    assert dn(12) == 1, '{} != 1'.format(dn(12))

    return dn(1) * dn(10) * dn(100) * dn(1000) * dn(10000) * dn(100000) * dn(1000000)