pwaS eht tirsf dna tasl setterl fo hace dorw

Question

Or, "Swap the first and last letters of each word"

Your challenge is to, given a string of alphabetical ASCII characters as well as one other character to use as a delimiter (to separate each word), swap the first and last letters of each word. If there is a one-character word, leave it alone.

The examples/testcases use the lowercase letters and the space as the delimiter.

You do not need to handle punctuation; all of the inputs will only consist of the letters a through z, separated by a delimiter, all of a uniform case.

For example, with the string "hello world":

Input string: "hello world"
Identify each word: "[hello] [world]"
Identify the first and last letters of each word: "[[h]ell[o]] [[w]orl[d]]"
Swap the first letters of each word: "[[o]ell[h]] [[d]orl[w]]"
Final string: "oellh dorlw"

NOTE: the delimiter does not need to be inputted separately. The delimiter is just the character used to separate words. It can be anything. I wanted to leave options open for creative golfers, so I did not want to limit it to just spaces or new lines. The delimiter is just a character that separates words in the input string.

Test cases:

"swap the first and last letters of each word" -> "pwas eht tirsf dna tasl setterl fo hace dorw"
"hello world" -> "oellh dorlw"
"test cases" -> "test sasec"
"programming puzzles and code golf" -> "grogramminp suzzlep dna eodc folg"
"in a green meadow" -> "ni a nreeg weadom"
"yay racecar" -> "yay racecar"

Answer 1

><> (Fish), 80 78 bytes

3:i&1+:i:'!'(?v$4p30.
$&p4{g4:-1v?(0/p4
. 1ap31'v'/
|.!00+1p4$' ':/
"/"
o>:?!;

Saved 2 bytes trying to fix handling 1-letter words

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Answer 2

Thunno 2 Ṡ, 6 bytes

OıḢsṾƤ

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Explanation

OıḢsṾƤ  # Implicit input
O       # Split on spaces
 ı      # Map over the list:
  Ḣ     #  Extract the first character
   s    #  Swap so the rest is on top
    Ṿ   #  Rotate it right once
     Ƥ  #  Append the first character
        # Join the list by spaces
        # Implicit output

Answer 3

Arturo, 37 bytes

$=>[replace&{/(\w)(\w*)(\w)}"$3$2$1"]

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Answer 4

JavaScript (Node.js), 72 bytes

Solution without regex = two times longer!

s=>s.split` `.map(w=>w[w.length-1]+w.slice(1,-1)+(w[1]?w[0]:"")).join` `

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---

More functional programming approach (81 bytes) :

s=>s.split` `.map(w=>[...w].map((c,i)=>i%(l=w.length-1)?c:w[l-i]).join``).join` `

Answer 5

Vyxal S, 31 bits^v2, 3.875 bytes

⌈ƛḣǔp

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Ports Thunno 2.

Explained

⌈ƛḣǔp
⌈ƛ     # To each word after splitting on spaces
  ḣ    #   Push the first character, then the rest
   ǔ   #   Rotate right once 
    p  #   Prepend to the first character
# The S flag joins on spaces.

Answer 6

C# (Visual C# Interactive Compiler), 90 bytes

n=>n.Split().Any(x=>WriteLine(x.Length<2?x:x.Last()+x.Substring(1,x.Length-2)+x[0])is int)

Uses newline as delimiter, though really any whitespace can be used.

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Answer 7

Icon, 76 bytes

link segment
procedure f(s)
w:=!seglist(s,' ')&w[1]:=:w[-1]&writes(w)&\x
end

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Answer 8

Java, 110 109 bytes

-1 bytes by using a newline for a delimeter

s->{int l;for(var i:s.split("\n"))System.out.println(i.charAt(l=i.length()-1)+i.substring(1,l)+i.charAt(0));}

TIO

Answer 9

Haskell, 75 74 bytes

Fixed a bug pointed at by Cubic and also golfed down 1 byte.

f=unwords.map(#v).words
x#g=g(r$tail x)++[x!!0]
r=reverse
v[]=[]
v x=r$x#r

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Answer 10

Scala, 100 bytes

(b:String,c:String)=>b.split(c)map(f=>f.tail.lastOption++:(f.drop(1).dropRight(1)+f.head))mkString c

Answer 11

T-SQL, 126 bytes

SELECT STRING_AGG(STUFF(STUFF(value,1,1,RIGHT(value,1)),LEN(value),1,LEFT(value,1)),' ')
FROM STRING_SPLIT((SELECT*FROM t),' ')

Input is via a pre-existing table t with varchar field v, per our IO standards.

Reading from back to front, STRING_SPLIT breaks a string into individual rows via a delimiter, STUFF modifies the characters at the specified positions, then STRING_AGG mashes them back together again.

Answer 12

Japt -S, 10 bytes

Convinced there has to be a shorter approach (and I was right) but this'll do for now.

¸ËhJDg)hDÌ

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¸ËhJDg)hDÌ     :Implicit input of string
¸              :Split on spaces
 Ë             :Map each D
  h            :  Set the character at
   J           :    Index -1 to
    Dg         :    The first character in D
      )        :  End set
       h       :  Set the first character to
        DÌ     :    The last character in D
               :Implicit output, joined by spaces

Answer 13

SNOBOL4 (CSNOBOL4), 90 bytes

I	R =
	INPUT LEN(1) . L REM . M	:F(END)
	M ARB . M RPOS(1) REM . R
	OUTPUT =R M L	:(I)
END

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Takes input separated by newlines; can be either uppercase or lowercase.

I R =					;* set R to empty string
  INPUT LEN(1) . L REM . M	:F(END)	;* take first character and set to L, and set the
					;* REMainder to M
  M ARB . M RPOS(1) REM . R		;* match an ARBitrary (possibly empty) run
					;* of characters to M up to but excluding the last character
					;* and save the last character to R
					;* if M is empty, (i.e., a one-letter word), then this fails 
					;* and nothing happens, so M remains empty and R remains empty
  OUTPUT =R M L	:(I)			;* output Right, Middle, Left, then goto I.
END

(previous version)

SNOBOL4 (CSNOBOL4), 92 bytes

I	R =M =
	INPUT LEN(1) . L ('' | ARB . M LEN(1) . R) RPOS(0)	:F(END)
	OUTPUT =R M L	:(I)
END

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This is thematically the same, clearly, but suffers from using FAILURE as the termination status, preventing us from using FAILURE as a no-op as we do in the above. This then forces us to set M = as well as R =, which is 3 bytes.

Answer 14

PowerShell, 50 bytes

-split"$args"|%{$_-replace'^(.)(.*)(.)$','$3$2$1'}

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Uses regex to replace each word with a captured first and last letter surrounding the original core. If it's a single character, replace will find nothing and leave it alone.

Answer 15

Python 2, 67 66 64 61 60 bytes

lambda s:' '.join(w[1:][-1:]+w[1:-1]+w[0]for w in s.split())

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_{-1 byte, thanks to squid}

_{-1 byte, thanks to Erik the Outgolfer}

---

Python 3, 63 61 58 57 bytes

print(*[w[1:][-1:]+w[1:-1]+w[0]for w in input().split()])

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Answer 16

PHP, 73 bytes

foreach(explode(' ',$argn)as$w){[$w[0],$w[-1]]=[$w[-1],$w[0]];echo"$w ";}

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Using PHP 7.1's Square bracket syntax for array destructuring to swap values.

Ungolfed:

foreach( explode( ' ', $argn ) as $w ) {
  [ $w[0], $w[-1] ] = [ $w[-1], $w[0] ];
  echo $w, ' ';
}

Answer 17

Jelly, 9 bytes

ḲṪ;ṙ1$Ɗ€K

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Explanation

ḲṪ;ṙ1$Ɗ€K | monadic link taking the string as input

Ḳ         | split at spaces
      Ɗ€  | for each word, do the following:
 Ṫ        | - pop the last letter
  ;ṙ1$    | - concatenate to the remaining letters rotated left once
        K | finally, join with spaces

Answer 18

Z80Golf, 43 bytes

00000000: 2100 c0cd 0380 3822 5745 cd03 8038 09fe  !.....8"WE...8..
00000010: 2028 0570 4723 18f2 736b 707e 23a7 2803   (.pG#..skp~#.(.
00000020: ff18 f87a ff3e 20ff 18d6 76              ...z.> ...v

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Corresponding assembly:

mainloop:
    ld hl, $c000
    call $8003
    jr c, hlt
    ld d, a
    ld b, l ; handle 1-character words
inputloop:
    call $8003
    jr c, endinput
    cp $20
    jr z, endinput
    ld (hl), b ; don't store the last character
    ld b, a
    inc hl
    jr inputloop
endinput:
    ld (hl), e ; always 0
    ld l, e
    ld (hl), b
outputloop:
    ld a, (hl)
    inc hl
    and a
    jr z, endoutput
    rst $38
    jr outputloop
endoutput:
    ld a, d
    rst $38
    ld a, $20
    rst $38
    jr mainloop
hlt:
    halt

Answer 19

Brainf**k, 126

>+[,[->>>+<+<+<]>----------[[-]<+>]>[[-]<<+>>]<<--[+<.<[[<]>>>[<.>>]<[<]>.<]>[>]>->>[.[-]<+>]<<<]>+[->>[-<<<+>>>]<+<]>[-<+>]<]

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Could definitely be golfed further.

Answer 20

C (gcc), 62 bytes

t;*s;f(int*i){for(s=i;*++i;i[1]>64||(t=*i,*i=*s,*s=t,s=i+2));}

I wanted to use a xor swap but that fails if a word is only one character long.

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Answer 21

brainfuck, 71 67 49 47 bytes

+[-[+>>]>[<<.[-]<[<]>>[.>]<[<]>[.[>]].>>>]<+<,]

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This code uses a few cheats, so i don't know if it is competing. The separator in the input is a 0x01. The input needs an extra trailing separator, otherwise the last word won't be printed.

code:

+[                  enter the loop / the first round only the last three commands of the main loop are interesting
  -[                if input is not 0x01
    +               restore character
    >>              go to exit if
  ]
  >[                else
    <<.[-]          print and delete last character
    <[<]>>[.>]      print all characters starting at the second
    <[<]>[.[>]]     print first character and go to end if word is longer than one character
    .               print null (space)
    >>>             leave a zero cell and go to exit else
  ]
  <+                set new else marker
  <                 go to new input location
  ,                 input next character
]

Answer 22

If halting is not necessary:

Aheui (esotope), 174 bytes

삭붵뱷뛰빠쇡붷뼤쎄투＠싼사쑫
ＢｙＬｅ쪼ｇｅｎ＠처쇠모코커
ＤＵＳＴ오멓＠＠＠＠푸셴쒼섣
＠＠＠＠쇡뽀＠＠＠삳멓＠샨＠맣

Try it online! press 'start' butten in TIO again to halt manually.

If halting is necessary:

Aheui (esotope), 225 bytes

살뷕볙눠쀄삭붵뱷뛰빠쇡붷빠쎄투＠싼사쑫
Ｂｙ＠＠＠＠＠야빠속＠＠＠수처쇠모오어
Ｌｅｇｅｎ＠＠먷초더헤셜썰뻐푸쉰썬＠셛
ＤＵＳＴ＠＠솩뽀사뫼섁쀠우삳멓산멓

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In this version, following space after input is necessary. fixed. Now it is OK to not finish with space.

Answer 23

Factor, 60 bytes

[ " "split [ 1 cut 1 short cut* spin 3append ] map " "join ]

This doesn't run on TIO (Try it Online) because spin postdates build 1525, the one TIO uses. Here's a screenshot of running it in build 1889, the official 0.98 release:

Explanation

It's a quotation (anonymous function) that takes a string from the data stack as input and leaves a string on the data stack as output. Assuming "in a green meadow" is on top of the data stack when this quotation is called...

Snippet	Comment	Data stack (the bottom is the top)
" "split	Split a string into a sequence of space-delimited strings	{ "in" "a" "green" "meadow" }
[ ... ] map	Apply a quotation to each element of a sequence, collecting the results in a new sequence of the same length
	Inside the quotation during the first iteration of map now...	"in"
1 cut	Split a string in two at index 1	"i" "n"
1 short	The minimum of 1 and the length of the sequence on top of the stack — prevents cut* from trying to cut at an invalid index	"i" "n" 1
cut*	Like cut, but works from the end of the sequence; not the start	"i" "" "n"
spin	Swap the object on top of the data stack with the third object from the top of the data stack	"n" "" "i"
3append	Append three sequences	"ni"
	And so forth...	{ "ni" "a" "nreeg" "weadom" }
" "join	Join a sequence of strings into a single string separated by a space	"ni a nreeg weadom"

Answer 24

Stax, 6 bytes

╡à⌂≤¬)

Run and debug it

Uses newline for the word delimiter

Answer 25

Lexurgy, 30 bytes

s:
[]$1 ([]*)$2 []$3=>$3 $2 $1

Answer 26

GolfScript, 19 15 bytes

-4 bytes by splitting on newlines

Input is taken seperated by newlines.

n/{[)\(]''+}%n*

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Explanation

n/{[)\(]''+}%n* # whole program
n/              # split the <implicit> input by newlines
    {        }% # for each value in the split input
     [)  ]      # take the last item of the string
       \        # swap stack ; stack: <last letter> <word without last letter>
        (       # take the first item out of the string ; stack: <last letter> <word> <first letter>
          ''+    # concatenate into charcodes
              n* # join by newlines

Answer 27

jq, 73 68 bytes

./" "|map((length<2//[./""|.[-1],.[1:-1][],.[0]]|add?)//.)|join(" ")

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How?

  . / " "                             # Split on spaces
| map(                                # For each word...
    (
         length<2                     # If it's shorter than 2 letters, emit false
      // [   . / ""                   # Otherwise, emit the word's characters
           | .[-1], .[1:-1][], .[0]]  # ...in the order last, middle, first
      | add?                          # Then re-join the characters into an updated word. If we don't have a list of characters, (if the original was too short), emit nothing
    ) // .                            # If we didn't get a value, emit the word unchanged
  )
| join(" ")