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Requirements:
Example:
Input: abcde
Output: abbcdde
Winning Criteria:
Standard code golf. Shortest number of bytes in program wins.
Clarification:
For languages with 1-based indexing the output must still match the above, aabccdee is not an acceptable solution.
d, 6 bytes♀J,⌡I►
Uncompressed:
2V2m-*M
Not a really good target for this challenge, I just feel that this is pretty fun to do.
Also the 1-indexed advantage seems to be a disadvantage here. If only W has a 0-index ...
% Note that W is one-indexed. (For the ease of the iterator protocols
% which have a 1-range as a built-in.)
V2m % Index of current item modulo 2
2 - % Subtract 2 by the number (effectively yields
% 1->1, 0->2 )
* % Repeat the character that many times
M % Do this for every item in the input
GolfScript doesn't have item count so you will need to do it yourself.
1:&;{]&):&2%)*}%
# Implicitly pushed input
1:&; # set count to 1
{ }% # foreach item of input
]&):& # add count by one
2%)* # repeat item by cnt % 2 + 1
Uses the same regex as @DigitalTrauma.
s=>s.replace(/.(.)/g,"$&$1")
A recursive version.
f=([a,b,...c])=>b?a+b+b+f(c):[a]
print(((...):gsub('.(.)','%0%1')))
Takes input as an argument, prints result to stdout. Every two characters are replaced with themselves and second one appended.
2a2x1v1x1f1r3x1v2e1o1r3x1v2e2o1f0x1x2f0a0x1f
Works for any input string terminated with the control character STX (U+0002).
Explanation (with 0x commands removed)
2a2x1v # Set variable 1 equal to 2
1x1f1r3x1v2e # Function 1
# Read a byte of input
# Jump to function 2 if it equals variable 1
1o # Otherwise, output it once
1r3x1v2e # Read another byte of input
# Jump to function 2 if it equals variable 1
2o # Otherwise, output it twice
1f # Jump back to the start of function 1
1x2f0a # Function 2
# Add 0 to the register
1f # Call function 1
[S S S T N
_Push_1][N
S S N
_Create_Label_LOOP][S S S T N
_Push_1][T S S S _Add][S S S T S N
_Push_2][T S T T _Modulo][S N
S _Dupe][S N
S _Dupe][S N
S _Dupe][S N
S _Dupe][T N
T S _Read_STDIN_as_character][T T T _Retrieve_input][T N
S S _Print_as_character][N
T S N
_If_0_Jump_to_Label_LOOP][T T T _Retrieve_input][T N
S S _Print_as_character][N
S N
N
_Jump_to_label_LOOP]
Letters S (space), T (tab), and N (new-line) added as highlighting only.
[..._some_action] added as explanation only.
Try it online (with raw spaces, tabs and new-lines only).
Explanation in pseudo-code:
Integer n = 1
Start LOOP:
n = (n+1) modulo-2
Integer c = STDIN as character
Print c as character to STDOUT
If(n == 0):
Go to the next iteration of LOOP
Print c as character to STDOUT
Go to the next iteration of LOOP
NSSN SSSTN TNST NSNN (create label (empty); push 1; pop and print as integer; jump to label (empty)). For an if-statement you'd have to make the value either 0 or negative, and use the conditional jumps. You usually do have to duplicate the value if you still need it later on however, since the conditional labels will pop the value.
\$\endgroup\$
Feb 6, 2020 at 17:55
Thanks to Malivil for 12 bytes !
s=>s.split``.map((v,i)=>i%2==1?v+v:v).join``
v.repeat(2) to v+v
\$\endgroup\$
2co{J[-j}\m
2co # Split into chunks of 2 {"ab" "cd" "e"}
{
J # Duplicate pair of chars
[- # Take the tail (returns empty for length 1 strings)
j # Swap to correct order for concat
}\m # For each pair, and then concatenate
2co)+.\[
Works for even length strings only
2co # Same as above
)+. # For each group append the last char again
\[ # Concatenate
-1 byte thanks to Bubbler
∊⊢⍴⍨¨1 2⍴⍨≢
A train that takes a string and returns a string (or any list technically).
⍴⍨ ⍝ Reshape
¨ ⍝ Each of
⊢ ⍝ The input
1 2 ⍝ To the array 1 2
⍴⍨ ⍝ Reshaped to
≢ ⍝ The length of the input
∊ ⍝ And flatten the result
: f 0 do dup dup 1 type i 2 mod type 1+ loop ;
: f \ start a new word definition
0 do \ loop from 0 to string-len - 1
dup dup \ duplicate the current character address twice
1 type \ output the current letter
i 2 mod type \ if odd, output again, if even do nothing (0 type = output nothing)
1+ \ increment current character address
loop \ end loop
; \ end word definition
(.(.))
\1\2
The first answer in my new language. It's a simple language based around python regex substitution
(.(.)) Replace each pair of characters with
\1\2 matching group 1 (both characters) followed by matching group 2 (the second character)
Try it online! (The second command line argument is input)
\0/$0 possible in Python or your language? I.e. .(.) and \0\1?
\$\endgroup\$
Feb 20, 2020 at 16:37
Saved a 3 bytes thanks to ceilingcat!!!
Saved a byte thanks to S.S. Anne!!!
i;f(c){for(i=0;~(c=getchar());printf(&c))c*=i++%2?257:1;}
c and i and initializing i at its definition.
\$\endgroup\$
Feb 3, 2020 at 17:29
listen to S
cut S
X's0
Y's0
while S-X
let S at X be*1+Y
let Y be not Y
let X be+1
join S
say S
Try it here (Code will need to be pasted in)
BEGIN{RS=".|";ORS=e}$0=NR%2?RT:RT RT
BEGIN{RS=".|";ORS=e} This reads one character at a time,
which can be retrieved by the RT variable.
$0=NR%2?RT:RT RT If NR=1 (mod 2), i.e., True, assigns "RT" to the output.
Otherwise, assigns "RT RT", which is RT concatenated to itself.
This conditional simply doubles the even occurrences.
WV(UWa!*h)
I love it when I can abuse built-in numbers for some other purpose.
WV(UWa!*h)
a First command-line argument
UW Unweave into a list of two strings, each containing every other character
h 100
!* Logically negate each digit
( ) Index into the list using each of those values
WV Weave the resulting list of three strings back together
For instance, if the input is abcde:
UWa ["ace"; "bd"]
!*h [0; 1; 1]
( ) ["ace"; "bd"; "bd"]
WV "abbcdde"
{S:g[.<(.]x=2}
Regex that matches every other character and substitutes it with itself string multiplied by 2.
¤+ōČōōČ
ōČ Take a character and print it.
ōōČ Take a character and print it twice.
¤+ Repeat this forever.
⭆Ｓ×ι⊕﹪κ²
Try it online! Link is to verbose version of code. Explanation:
Ｓ Input string
⭆ Map over characters and join
² Literal 2
κ Current index
﹪ Modulo
⊕ Incremented
ι Current character
× Repeated
Implicitly print
This was easy, but also fun!
{@eachargv.0}{@echo_}{@if__ is mod2}{@echo_}
Loops through all the characters, and checks if the index of the character (__) is not a multiple of 2 (odd). If it isn't a multiple of 2, outputs it again.
Ungolfed:
Just in case you are curious.
{@each argv.0 as char key key}
{@echo char}
{@if key is not multiple of 2}
{@echo char}
{@/}
{@/}
as char is optional, using the variable _ by default, to hold the array item/character from the string.key key is optional, using the variable __ by default, to hold the index.{@/} ae optional and safe to remove.You can try it on http://sandbox.onlinephpfunctions.com/code/5fc880374f58b72c4dc3ee2c573349e7a218aed8 You can check and try both golfed and ungolfed versions.
Assuming your string are all alphabetically sorted, you can use:
lambda x:''.join(sorted(x[1::2]*2+x[::2]))
function b($i){$c=0;$o;$i.ToCharArray().ForEach{if($c%2-eq1){$o+="$_$_"}else{$o+="$_"}$c++;};write $o}
p:parse((c={1}))parse((c={1 1}))\p;c:smark any(!<<>>)scopy;
1as the first character, for the benefit of languages with1-based indexing? \$\endgroup\$