Code Golf - Word Scrambler

Question

Please answer with the shortest possible source code for a program that converts an arbitrary plaintext to its corresponding ciphertext, following the sample input and output I have given below. Bonus points* for the least CPU time or the least amount of memory used.

Example 1:

Plaintext: The quick brown fox jumps over the lazy dog. Supercalifragilisticexpialidocious!

Ciphertext: eTh kiquc nobrw xfo smjup rvoe eth yalz .odg !uioiapeislgriarpSueclfaiitcxildcos

Example 2:

Plaintext: 123 1234 12345 123456 1234567 12345678 123456789

Ciphertext: 312 4213 53124 642135 7531246 86421357 975312468

Rules:

1. Punctuation is defined to be included with the word it is closest to.
2. The center of a word is defined to be ceiling((strlen(word)+1)/2).
3. Whitespace is ignored (or collapsed).
4. Odd words move to the right first. Even words move to the left first.

You can think of it as reading every other character backwards (starting from the end of the word), followed by the remaining characters forwards. Corporation => XoXpXrXtXoX => niaorCoprto.

Thank you to those who pointed out the inconsistency in my description. This has lead many of you down the wrong path, which I apologize for. Rule #4 should clear things up.

*Bonus points will only be awarded if Jeff Atwood decides to do so. Since I haven't checked with him, the chances are slim. Sorry.

Answer 1

Python, 50 characters

For input in i:

' '.join(x[::-2]+x[len(x)%2::2]for x in i.split())

Alternate version that handles its own IO:

print ' '.join(x[::-2]+x[len(x)%2::2]for x in raw_input().split())

A total of 66 characters if including whitespace. (Technically, the print could be omitted if running from a command line, since the evaluated value of the code is displayed as output by default.)

---

Alternate version using reduce:

' '.join(reduce(lambda x,y:y+x[::-1],x) for x in i.split())

59 characters.

Original version (both even and odd go right first) for an input in i:

' '.join(x[::2][::-1]+x[1::2]for x in i.split())

48 characters including whitespace.

Another alternate version which (while slightly longer) is slightly more efficient:

' '.join(x[len(x)%2-2::-2]+x[1::2]for x in i.split())

(53 characters)

Answer 2

For an input in s:

f=lambda t,r="":t and f(t[1:],len(t)&1and t[0]+r or r+t[0])or r
" ".join(map(f,s.split()))

Python, 90 characters including whitespace.

Answer 3

Perl, 78 characters

For input in $_. If that's not acceptable, add six characters for either $_=<>; or $_=$s; at the beginning. The newline is for readability only.

for(split){$i=length;print substr$_,$i--,1,''while$i-->0;
print"$_ ";}print $/

Answer 4

Python - 69 chars

(including whitespace and linebreaks)

This handles all I/O.

for w in raw_input().split():
 o=""
 for c in w:o=c+o[::-1]
 print o,

Answer 5

J, 58 characters

>,&.>/({~(,~(>:@+:@i.@-@<.,+:@i.@>.)@-:)@<:@#)&.><;.2,&' '

Answer 6

Haskell, 64 characters

unwords.map(map snd.sort.zip(zipWith(*)[0..]$cycle[-1,1])).words

Well, okay, 76 if you add in the requisite "import List".

Answer 7

Lua

130 char function, 147 char functioning program

Lua doesn't get enough love in code golf -- maybe because it's hard to write a short program when you have long keywords like function/end, if/then/end, etc.

First I write the function in a verbose manner with explanations, then I rewrite it as a compressed, standalone function, then I call that function on the single argument specified at the command line.

I had to format the code with <pre></pre> tags because Markdown does a horrible job of formatting Lua.

Technically you could get a smaller running program by inlining the function, but it's more modular this way :)

t = "The quick brown fox jumps over the lazy dog. Supercalifragilisticexpialidocious!"
T = t:gsub("%S+", -- for each word in t...
                  function(w) -- argument: current word in t
                    W = "" -- initialize new Word
                    for i = 1,#w do -- iterate over each character in word
                        c = w:sub(i,i) -- extract current character
                        -- determine whether letter goes on right or left end
                        W = (#w % 2 ~= i % 2) and W .. c or c .. W
                    end
                    return W -- swap word in t with inverted Word
                  end)


-- code-golf unit test
assert(T == "eTh kiquc nobrw xfo smjup rvoe eth yalz .odg !uioiapeislgriarpSueclfaiitcxildcos")

-- need to assign to a variable and return it,
-- because gsub returns a pair and we only want the first element
f=function(s)c=s:gsub("%S+",function(w)W=""for i=1,#w do c=w:sub(i,i)W=(#w%2~=i%2)and W ..c or c ..W end return W end)return c end
--       1         2         3         4         5         6         7         8         9        10        11        12        13
--34567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
-- 130 chars, compressed and written as a proper function

print(f(arg[1]))
--34567890123456
-- 16 (+1 whitespace needed) chars to make it a functioning Lua program, 
-- operating on command line argument

Output:

$ lua insideout.lua 'The quick brown fox jumps over the lazy dog. Supercalifragilisticexpialidocious!'
eTh kiquc nobrw xfo smjup rvoe eth yalz .odg !uioiapeislgriarpSueclfaiitcxildcos

I'm still pretty new at Lua so I'd like to see a shorter solution if there is one.

---

For a minimal cipher on all args to stdin, we can do 111 chars:

for _,w in ipairs(arg)do W=""for i=1,#w do c=w:sub(i,i)W=(#w%2~=i%2)and W ..c or c ..W end io.write(W ..' ')end

But this approach does output a trailing space like some of the other solutions.

Answer 8

Bash - 133, assuming input is in $w variable

Pretty

for x in $w; do 
    z="";
    for l in `echo $x|sed 's/\(.\)/ \1/g'`; do
        if ((${#z}%2)); then
            z=$z$l;
        else
            z=$l$z;
        fi;
    done;
    echo -n "$z ";
done;
echo

Compressed

for x in $w;do z="";for l in `echo $x|sed 's/\(.\)/ \1/g'`;do if ((${#z}%2));then z=$z$l;else z=$l$z;fi;done;echo -n "$z ";done;echo

Ok, so it outputs a trailing space.

Answer 9

C, 140 characters

Nicely formatted:

main(c, v)
  char **v;
{
  for( ; *++v; )
  {
    char *e = *v + strlen(*v), *x;
    for(x = e-1; x >= *v; x -= 2)
      putchar(*x);
    for(x = *v + (x < *v-1); x < e; x += 2)
      putchar(*x);
    putchar(' ');
  }
}

Compressed:

main(c,v)char**v;{for(;*++v;){char*e=*v+strlen(*v),*x;for(x=e-1;x>=*v;x-=2)putchar(*x);for(x=*v+(x<*v-1);x<e;x+=2)putchar(*x);putchar(32);}}

Answer 10

TCL

125 characters

set s set f foreach l {}
$f w [gets stdin] {$s r {}
$f c [split $w {}] {$s r $c[string reverse $r]}
$s l "$l $r"}
puts $l