countdown

countdown.py

import sys
import re


def find_repr(target, numbers):
    org_reprs = dict((number, str(number)) for number in numbers)
    curr_reprs = org_reprs
    while target not in curr_reprs:
        old_reprs, curr_reprs = curr_reprs, {}
        for x in old_reprs:
            for y in org_reprs:
                repr_x, repr_y = old_reprs[x], old_reprs[y]
                curr_reprs[x + y] = '(%s) + (%s)' % (repr_x, repr_y)
                curr_reprs[x - y] = '(%s) - (%s)' % (repr_x, repr_y)
                curr_reprs[x * y] = '(%s) * (%s)' % (repr_x, repr_y)
                if y > 0 and x % y == 0:
                    curr_reprs[x // y] = '(%s)/(%s)' % (repr_x, repr_y)
                    curr_reprs.update(old_reprs)
    return curr_reprs[target]


if __name__ == '__main__':

    args = sys.argv[1:]
    numbers = [int(a) for a in args]
    if len(args) != 7:
        print('Usage: ./program <arg1> <arg2> <arg3> <arg4> <arg5> <arg6> <arg7>')
    else:
        result = find_repr(numbers[6], numbers[:6]) + ' = {}'.format(numbers[6])
        print(result)