sum bool clear solution for The Secret Room by Phil15 - python coding challenges

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sum bool solution in Clear category for The Secret Room by Phil15

BELOW_20 = [None, 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight',
            'nine', 'ten', 'eleven', 'twelve', 'thirteen', 'fourteen', 'fifteen',
            'sixteen', 'seventeen', 'eighteen', 'nineteen']
TENS = ['twenty', 'thirty', 'forty', 'fifty', 'sixty', 'seventy', 'eighty', 'ninety']

def word(nb):
    """Write numbers 1 to 1000 in words (and 0 --> '')."""
    if 0 <= nb < 20:
        res = [BELOW_20[nb]]
    elif 20 <= nb < 100:
        tens, below_ten = divmod(nb, 10)
        res = [TENS[tens - 2], BELOW_20[below_ten]]
    elif 100 <= nb < 1000:
        hundreds, below_hundred = divmod(nb, 100)
        res = [BELOW_20[hundreds], 'hundred', word(below_hundred)]
    else:
        res = ['one', 'thousand']
    return ' '.join(elem for elem in res if elem) # remove possible None / 0.

secret_room = lambda door: sum(word(nb) < word(door) for nb in range(door))

Sept. 11, 2018

Comments:

Phil15 on Sept. 11, 2018, 9:19 a.m.
if you don't like I call word(door) for each bool in the sum of secret_room, just add <pre class='brush: python'>from functools import lru_cache @lru_cache(4) # for word function remembering the last 4 calls. Then word(door) is in memory. def word(nb): ... </pre>

serg3y1999 on Oct. 3, 2018, 6:44 a.m.
can you explain how works secret_room = lambda door: sum(word(nb) < word(door) for nb in range(door)) ?

Phil15 on Oct. 3, 2018, 9:45 a.m.
Yes I can. First, if you don't know very well lambdas, it's like <pre class='brush: python'>def secret_room(door): return sum(word(nb) < word(door) for nb in range(door)) </pre> We are looking for the number of the given door, so we need to know how many doors there are before the given one. "word(nb) < word(door)" is a boolean but in sum, it gives us 1 if it's true else 0. So I sum 1s and 0s, so I count how many doors there are before the given door. Well, there is a subtlety. nb is taken in range(door) so 0, 1, 2, ... door-1. The subtlety is I consider 0. (word(0)=='' is < anything.) It's because of "The count starts from the 1st position (not from the 0th)." in text explanation.

serg3y1999 on Oct. 10, 2018, 6:54 p.m.
thx !

Escher

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