6-liner: without str clear solution for Number Length by przemyslaw.daniel - python coding challenges

Enable Javascript in your browser and then refresh this page, for a much enhanced experience.

6-liner: without str solution in Clear category for Number Length by przemyslaw.daniel

def number_length(number: int) -> int:
    base, result = 10, 1
    while base <= number:
        base = (base << 3) + (base << 1)
        result += 1
    return result

Feb. 27, 2020

Comments:

sashisushi on April 4, 2020, 9:39 a.m.
How does it work? I didn't get the zero fill left shifting in this solution. Could you explain?

przemyslaw.daniel on April 8, 2020, 10:08 a.m.
To understand it better just try to print base and result before and at the end of the loop. This is example output for number_length(3231) <pre class='brush: python'>base=10, result=1 base=100, result=2 base=1000, result=3 base=10000, result=4 </pre> We repeat multiplication base by 10 (line #4) until it is less or equal number. The fast way to multiply by 10 is to use bit shifting

Nick_Paholnitski on April 27, 2020, 7:10 p.m.
I don't know why to do this, but it's intresting decision

Jjjlkk on July 1, 2020, 8:40 a.m.
I like very much this way of multiplying! Thanks :)

Sukotto on Aug. 23, 2020, 12:56 p.m.
Took me about 30 minutes to write this on paper, going through the loop to figure out what was happening, especially as i'm not too familiar with bit operators. Such a strange way of solving a problem, it's the first practical use of this technique i've seen though.

mohammad.moaddi on Aug. 24, 2020, 7:30 a.m.
num << 3 + num << 1 == num * 8 + num * 2 = num*(10) I hope this helps :)

jideutomi on Sept. 4, 2020, 4:24 p.m.
This is so interesting. And still completely confusing for me. But makes me excited to learn it!

jiaoxueyuan1108 on Dec. 6, 2020, 9:40 a.m.
this is neat! Does it run faster on big input?

djw0514 on Feb. 7, 2021, 2:37 p.m.
base<<3 equivalent to base8 base<<2 equivalent to base2, so (base<<3) + (base<<1) equivalent to base*10, it's amazing.

Teja_002 on March 15, 2021, 6:42 a.m.
WOW!!!. I don't even know that there exists something called bitwise operators in python. Learned about it and took me a lot of time to understand what exactly is happening. Thanks a lot!. You're a genius.

Vitali_Drozd on March 19, 2021, 8:23 a.m.
Doesn't work for negative numbers.

przemyslaw.daniel on March 19, 2021, 10:09 a.m.
"You have a positive integer"

ChromeBrainer on April 7, 2021, 8:38 a.m.
got to learn new thing in python that i was not familiar with at all! shift operators work easy like that coding!

emadharazi11_93668302487544de8 on April 12, 2021, 8:28 a.m.
This is brilliant. Learnt something new, thanks!

Ajay99 on May 2, 2021, 12:01 p.m.
I don't know how this worked or just say I am not able to understand this code but I have to admit your solution is unique and I doubt that anyone goes for that solution in their first thought.

chloe88huang on May 15, 2021, 7:59 a.m.
Is it the same as using base *= 10 on line 4?

przemyslaw.daniel on May 16, 2021, 4:31 p.m.
base = (base << 3) + (base << 1) = base * 8 + base * 2 = base * 10

Zack_ZHAO on Oct. 9, 2021, 2:32 a.m.
Thanks for your kind reply! What a amazing math solution.

mevaere on June 14, 2021, 12:32 p.m.
<h1>It's not faster.</h1> <pre class='brush: python'>from timeit import timeit import random def number_length(a: int) -> int: return len(str(a)) def number_length2(number: int) -> int: base, result = 10, 1 while base <= number: base = (base << 3) + (base << 1) result += 1 return result liste = [random.randint(1, 2000000000000000000) * i for i in range(10000)] print(timeit('[number_length(i) for i in liste]', setup='pass', number=1000, globals=globals())) print(timeit('[number_length2(i) for i in liste]', setup='pass', number=1000, globals=globals())) </pre> <ul> <li>number_length : 2.42s</li> <li>number_length2 : 21.37s</li> </ul>

przemyslaw.daniel on Aug. 19, 2021, 3:47 p.m.
you might be right. The solution is fast in case of low level languages like C/C++ but in python interpreter comes into play

sanjieyu on June 28, 2021, 12:26 a.m.
I can't understand firstly, I think this is a maths solution :)

vincent.thai on Sept. 17, 2021, 1:40 p.m.
sweaty

sachin-bhat on Oct. 21, 2021, 1:20 a.m.
A chuncky solution indeed! But still, it definitely looks great!

sachin-bhat on Oct. 21, 2021, 1:22 a.m.
A chunky solution (in terms of speed) indeed! But still, it definitely looks great!

dronhund_9509254485c24503afa27 on Aug. 13, 2022, 11:06 p.m.
bit shifting, not sure if its most pythonic way but its certanly cool

Tapas_Kohad on Nov. 23, 2023, 10:50 a.m.
spent months coding in c, 2 years learning python in free time as a hobby. didn't come to know about the '>>' that you used. thanks

kastannie on July 2, 2024, 10:23 a.m.
LMAOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO

jrchionis on July 16, 2024, 11:35 a.m.
Reading your code has been educational for me as a beginner. According to the comments, the bit shifting approach doesn't actually improve performance in interpreted languages, while it hypothetically would in compiled, "lower level" ones. I'll need to learn more about why this might be the case at some point, but for now, I can feel satisfied having acquiring this titillating little tidbit ^__^ .

Strings and Integers

0 %

You ClassRoom Demo is Ready With the new tool CheckiO ClassRoom, you will be able to analyze your students' progress, have your own leaderboard, change missions order on the map, and so on.