61 votes
Accepted

Binary to decimal converter

Jelly, 5 bytes DḤ+¥/ Try it online! Explanation The cast D is a monad (single argument function): digits, turning ...
  • 66.2k
38 votes

Output numbers up to 2^n-1, "sorted"

Python, 53 bytes f=lambda n,i=1:n*[f]and[i]+f(n-1,2*i)+i%2*f(n-1,i-~i) Try it online! The recursive function generates the sorted list as a pre-order walk down ...
  • 139k
33 votes

xkcd-Style Page Numbering

CJam, 24 23 22 21 19 bytes ri_)2b,,W%{2\#(md}/ This is an O(log n) approach, where n is the input, that completes the last test case instantly. It converts n ...
  • 207k
28 votes

xkcd-Style Page Numbering

Python 2, 67 bytes def f(n):x=len(bin(n+1))-3;y=2**x-1;return n and n/y*10**~-x+f(n%y) Seems to work for the given test cases. If I've got this right, this ...
  • 61.1k
27 votes

Find the polynomial

Jelly, 3 bytes ‘b@ Try it online! Returns the polynomial as a list of coefficients. Since we know the polynomial has non-negative integer coefficients, f(b) ...
  • 70.6k
26 votes

What base is this number in?

Python, 27 22 bytes lambda s:(max(s)-8)%39 This requires the input to be a bytestring (Python 3) or a bytearray (Python 2 and 3). Thanks to @AleksiTorhamo for ...
  • 207k
26 votes
Accepted

Converting "0xUsernames"

05AB1E, 4 bytes D1ìH Explanation ...
  • 1,328
23 votes

Balanced Ternary Converter

Python 2: 58 chars n=input() s="" while n:s="0+-"[n%3]+s;n=-~n/3 print s or 0 Generates the balanced ternary digit-by-digit from the end. The last digit is given ...
  • 139k
22 votes
Accepted

Numbers that are actually letters

Pyth, 43 - 40 = 3 bytes ?&K@J.HQG-JG"Mix"%"Only %sers"?K"lett""numb Test suite This achieves the bonus. Only numbers and ...
  • 41.4k
22 votes

Binary to decimal converter

Python 2, 49 37 31 30 Bytes Now this will take a binary number in a decimal representation, since Python can handle arbitrarily large integers. ...
  • 7,752
21 votes
Accepted

16-bit binary grid

J, 26 bytes (' ';' # '){~4 4$_16{.#: An anonymous verb. Thankfully, J is very good at drawing boxes. Let's try it out: ...
  • 66.2k
21 votes

Reverse and square

Mathematica, 42 21 bytes Thanks to alephalpha for halving the score. #~IntegerReverse~2^2& The actual reason I did this in Mathematica was because I wanted ...
21 votes

What base is this number in?

Python, 25 bytes lambda x:int(max(x),36)+1 Defines a lambda that takes the string x. Finds the largest digit in the string (...
  • 7,684
21 votes

What is the reverse (binary) bit number?

Python, 29 bytes lambda n:int(bin(n)[:1:-1],2) Try it online! This is an anonymous, unnamed function which returns the result. First, ...
  • 14k
21 votes

The best base is 10... Let's reach it!

Mathematica, 56 bytes #//.x_/;(b=Max[d=IntegerDigits@x]+1)<11:>d~FromDigits~b& Try it online! (Using Mathics.) I thought I'd check out what the ...
19 votes

Converting "0xUsernames"

JavaScript (ES6), 15 bytes s=>'0x1'+s-0||s How it works '0x1'+s converts the input into a literal hexadecimal string with ...
19 votes

Convert a 32 bit binary IPv4 address to its quad-dotted notation

x86-16 machine code, IBM PC DOS, 54 47 45 bytes Binary: ...
  • 11.2k
18 votes

Output numbers up to 2^n-1, "sorted"

Jelly, 6 bytes Ḷ2*ẆS€ This qualifies for the imaginary bonus. Try it online! How it works ...
  • 207k
18 votes

Does base n have any Rotate-Left-Double numbers?

05AB1E, 6 5 bytes ÍD<&Ā -1 byte thanks to @xnor and @Noodle9. Try it online or verify the first \$[2,100]\$ test cases. Explanation: ...
17 votes

Zeroes in interval

Jelly, 1 byte ¬ This uses base k+2, in which case there's a single 0 iff i is 0. It takes ...
  • 21.2k
17 votes
Accepted

What base is this number in?

Jelly, 4 bytes ṀØBi Requires uppercase. Try it online! or verify all test cases. How it works ...
  • 207k
17 votes

What is the reverse (binary) bit number?

Python, 29 bytes lambda n:int(bin(n)[:1:-1],2) Try it online
  • 23k
17 votes

French license plates

Pure Bash (no external utils), 64 2 bytes saved thanks to @NahuelFouilleul x={A..Z} eval f=($x$x-%03d-$x$x) printf ${f[$1/1000]} $[$1%1000] Try it online! - ...
16 votes
Accepted

Obfuscating text by cycling ternary digits

Pyth, 23 22 bytes sXc.<sXz=+GdJ^UK3K1KJG Try it online: Regular Input / Test Suite Thanks to @isaacg for one byte. Explanation: ...
  • 21.8k
16 votes
Accepted

Take a byte out of it!

Jelly, 6 bytes BḄ-8ƤṀ A monadic link taking a number and returning a number. Try it online! How? Uses a nice quick, Ƥ, ...
15 votes

Convert RGB integer value into RGB values

AVR ABI, 0 Quantities larger than the registers in the AVR's registers are represented with multiple registers. So, when passing in a 32-bit 'n' to a function, it is passed as 4x8-bit registers. ...
  • 261
15 votes

Numbers that are actually letters

Pyth, 6 bytes !-.HQG .HQ # Converts the input to hexadecimal - G # Deletes all letters ! # If empty, output True, else False Test it here
  • 43.5k
15 votes

Smallest Zeroless Base

Pyth, 6 bytes f*FjQT Verify all the test cases. How it works f*FjQT ~ Full program. f ~ First positive integer where the condition is truthy. jQT ~ ...
  • 41.6k
15 votes

Up go the bits!

Python 2, 31 bytes f=lambda n:n and 3*f(n/2)+n%2+1 Try it online!
  • 207k
14 votes

Convert RGB integer value into RGB values

Java 35 31 bytes. Yay!!! A java answer under 40 bytes. new int[]{n>>16,n>>8&255,n&255} Interestingly, java integers are always stored as ...
  • 11.4k

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