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Challenges

Reverse an ASCII string

+10
−0

Your goal is to reverse an ascii string. Given a (optionally newline or null terminated) input, output your input in reverse order, optionally followed by a newline. Terminate afterward. Function answers will not be given a newline, and are not expected to output one unless they print the answer to console.

Examples

Assume all inputs are followed by a newline, and are all standard ASCII encoded.

abcdef -> fedcba
Hello, World! -> !dlroW ,olleH
racecar -> racecar

Example program

function solution(x) {
    return x.split("").reverse().join("");
}

Further clarifications

  • No, you don't have to handle nulls correctly.
  • Nor empty inputs.
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General comments (7 comments)

25 answers

+7
−0

Ahead, 3 bytes

SW@

S    Slurp entire input to stack
 W   Write entire stack
  @  End

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General comments (2 comments)
+7
−0

Brain-Flak, 12 bytes

{({}<>)<>}<>

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# (Implicitly) Read characters from STDIN and place them all on the active stack

# While the top of the active stack is not null...
{
    # Push the following value on to the active stack
    (
        # Pop the current character off the active stack and add it to the value we're tracking
        {}
        
        # Toggle which stack is active
        <>
    # (push)
    )

    # Toggle back to the stack the input was on
    <>

# (endwhile)
}

# Toggle stacks back so that the secondary stack is active when the program ends
<>

# (Implicitly) Print all values on the active stack
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+6
−0

JavaScript, 25 24 bytes

-1 byte thanks to @Arnauld‭

f=([a,...b])=>a?f(b)+a:b

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General comments (2 comments)
+5
−0

jq, 16 bytes, preferably -rR

./""|reverse|add

Annoyingly, jq has convenient things like implicit I/O, and annoying things like adding strings, but you can't reverse a string >:|.

./""&add are slightly shorter than the more obvious split("")&join(""). The division operator splits a string, and add adds all the elements of an array together, using string concatenation in this case.

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+5
−0

C (gcc), 34 bytes

f(char*s){*s&&f(s+1)^putchar(*s);}

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Alternative:

C (gcc), 35 bytes

f(s){read(0,&s,1)&&f()^putchar(s);}

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Alternative #2:

C (gcc), 36 bytes

f(s){write(read(0,&s,1)&&f(),&s,1);}

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+5
−0

C, 66 59 bytes

-7 bytes thanks to Lundin!


In-place string reversal

f(char*s){s[1]?f(s+1):0;for(char t=*s;s[1];*++s=t)*s=s[1];}

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General comments (4 comments)
+4
−0

Python 3, 20 bytes

print(input()[::-1])

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+4
−0

C (gcc), 62 bytes

main(){char b[99],*p=strchr(gets(b),0);for(;p-->b;)putch(*p);}

This relies on the usual gcc extension abuse. It assumes that max user input is 98 characters + null term, since this wasn't specified.


EDIT: Revisited, function-based equivalent of the above (plus I have no idea what compiler I used to get putch working, not gcc/Linux at least):

C (gcc), 53 bytes

*o;f(char*s){for(s=strchr(o=s,0);s-->o;)putchar(*s);}

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General comments (1 comment)
+4
−0

Japt, 1 byte

w

Uh... yeah. Probably similar solutions for many other golf langs.

Try it

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+4
−0

Shakespeare Programming Language, 184 bytes

,.Ajax,.Puck,.Act I:.Scene I:.[Enter Ajax and Puck]Scene V:.Puck:Open mind!Be you worse zero?If soLet usScene L!Remember you!Let usScene V!Scene L:.Puck:Recall!Speak thy!Let usScene L!

Surprisingly short for SPL. Errors out with a runtime.

Adds input to the stack, then recalls it. Since SPL handles one character at a time, this automatically reverses the input. SPL also has a built-in function, where if there is no input, it will return -1, which allows us to see the end of input.

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+3
−0

Laser, 9 bytes

c⌜ps
 \U#

My own language's showcase time! This is a 2D language with an instruction pointer initially pointing to the right. It takes implicit input as an array of characters.

Explanation:

c⌜p    repeat as long as the current stack (input) isn't empty:
   s   pop from the current stack and push onto the next stack (the instruction pointer then loops back around to the c)

 ⌜
 \U#   once the current stack is empty, switch direction, get bounced to the right on the second line, move up a stack, and output it
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+3
−0

PowerShell, 43 bytes

param($s)(($s=$s|% t*y)|%{$s[--$q]})-join''

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+3
−0

Scala, 9 bytes

_.reverse

Try it in Scastie!

Explanation:

_.reverse
_          //The function argument
 .         //Call a method
  reverse  //Reverse the string
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+3
−0

Turing Machine.io, 363 bytes

0 0 0 0 -1 8 0
0 8 4 0 1 9 0
0 9 -1 0 0 1 0
0 1 0 0 1 9 0
1 1 1 0 1 9 0
2 1 2 0 1 9 0
3 1 0 0 -1 2 0
2 2 2 0 -1 3 0
0 3 0 0 -1 3 0
1 3 1 0 -1 3 0
2 3 2 0 1 4 0
0 4 0 0 -1 4 0
1 4 1 0 -1 4 0
2 4 2 0 1 5 0
0 5 0 1 1 5 0
1 5 1 1 1 5 0
2 5 2 2 -1 6 0
0 6 0 0 -1 6 0
1 6 0 0 -1 6 0
2 6 2 0 -1 7 0
4 6 4 0 0 7 1
0 7 0 0 -1 7 0
1 7 1 0 -1 7 0
2 7 2 0 1 5 0
4 7 4 0 1 5 0

This is probably very golf-able. I'll golf this down and add an explanation later.

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+3
−0

Perl 5 -p, 10 bytes

$_=reverse

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+2
−0

Bash, 3 bytes

rev

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Less boring:

Bash, 8 bytes

tac -rs.

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+2
−0

Befunge-98, 45 39 37 33 29 21 bytes

v:~<
>a-|
>v$<
,:
^_@

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This answer probably sucks :P

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General comments (2 comments)
+2
−0

Ruby, 14 bytes

->s{s.reverse}

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a straightforward builtin.

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+2
−0

Sclipting, (UTF-16) 2 bytes

Yay for builtins~

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+2
−0

Haskell, 7 bytes

reverse

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