Solutions to this blog post

gistfile1.py

"""https://blog.svpino.com/2015/05/08/solution-to-problem-5-and-some-other-thoughts-about-this-type-of-questions"""
from itertools import permutations, product


def problem1():
    def forloop(numbers):
        s = 0
        for number in numbers:
            s += number
        return s

    def whileloop(numbers):
        s = 0
        current_index = 0
        while current_index < len(numbers):
            s += numbers[current_index]
            current_index += 1
        return s

    def recursion(numbers):
        if len(numbers) == 0:
            return 0
        return numbers[0] + recursion(numbers[1:])

    l = [1, 2, 3, 4]
    expected_sum = sum(l)

    forloop_sum = forloop(l)
    whileloop_sum = whileloop(l)
    recursion_sum = recursion(l)

    print "problem 1:"

    print "forloop sum: {}".format(forloop_sum)
    assert forloop_sum == expected_sum

    print "whileloop sum: {}".format(whileloop_sum)
    assert whileloop(l) == expected_sum

    print "recursion sum: {}".format(recursion_sum)
    assert recursion(l) == expected_sum


def problem2():
    expected = ['a', 1, 'b', 2, 'c', 3]

    l1 = ['a', 'b', 'c']
    l2 = [1, 2, 3]

    flatten = lambda l: [i for sublist in l for i in sublist]

    combined = flatten(zip(l1, l2))

    print "problem 2:"
    print "solution is {}".format(combined)

    assert combined == expected


def problem3():
    def fibo(n):
        fibz = [0, 1]
        while len(fibz) < 100:
            fibz.append(fibz[-1] + fibz[-2])
        return fibz

    fib100 = fibo(100)

    print "problem 3:"
    print "solution is {}".format(fib100)

    assert len(fib100) == 100


def problem4():
    all_permutations = lambda l: [p for p in permutations(l)]
    concat_to_int = lambda l: int("".join([str(i) for i in l]))

    test_input = [50, 2, 1, 9]
    solution = max([concat_to_int(i) for i in all_permutations(test_input)])

    print "problem 4:"
    print "solution is {}".format(solution)

    assert solution == 95021


def problem5():

    # really slow utility funcs
    flatten = lambda l: [i for sublist in l for i in sublist]
    stringify = lambda t: "".join(flatten([str(i) for i in flatten(t)])).replace(" ", "")
    only_sum_100 = lambda l: [i for i in l if eval(i) == 100]

    nums = range(1, 9)
    chars = ["+", "-", " "]

    steps = [[x for x in product([str(j)], chars)] for j in nums]
    all_combos = [i for i in product(*[step for step in steps])]
    all_possibilities = [stringify(combo) + "9" for combo in all_combos]

    all_equaling_100 = only_sum_100(all_possibilities)

    print "problem 5:"
    print "solutions are {}".format(all_equaling_100)
    print all_equaling_100

    assert len(all_equaling_100) == 11


if __name__ == "__main__":
    problem1()
    problem2()
    problem3()
    problem4()
    problem5()