Palindrome Golf

Answer 1

Straightforward implementation in C using standard library functions, inspired by the strlen in the other C answer.

Number of characters: 57

p(char*s){char*r=strdup(s);strrev(r);return strcmp(r,s);}

Confession: I'm being the bad guy by not freeing r here. My current attempt at being good:

p(char*s){char*r=strdup(s);s[0]=strcmp(strrev(r),s);free(r);return s[0];}

brings it to 73 characters; I'm thinking of any ways to do it shorter.

Answer 2

Lua aims more at readability than conciseness, yet does an honest 37 chars:

function p(s)return s==s:reverse()end

variant, just for fun (same size):

p=function(s)return s==s:reverse''end

The JavaScript version is more verbose (55 chars), because it doesn't has a string reverse function:

function p(s){return s==s.split('').reverse().join('')}

Answer 3

Without using any library functions (because you should really add in the #include cost as well), here's a C++ version in 96:

int p(char*a,char*b=0,char*c=0){return c?b<a||p(a+1,--b,c)&&*a==*b:b&&*b?p(a,b+1):p(a,b?b:a,b);}

Answer 4

18 character perl regex

/^(.?|(.)(?1)\2)$/

Answer 5

Isn't using the reverse function in your language kind of cheating a bit? I mean, looking at the Ruby solution give as

def p(a)a==a.reverse end

you could easily rewrite that as

def p(a)a==a.r end

and just say that you made an extension method in your code so that "r" called reverse. I'd like to see people post solutions that don't contain calls to other functions. Of course, the string length function should be permitted.

Ruby without reverse - 41 characters

def m(a)a==a.split('').inject{|r,l|l+r}end

VB.Net - 173 Chars

Function P(ByVal S As String) As Boolean
    For i As Integer = 0 To S.Length - 1
        If S(i) <> S(S.Length - i - 1) Then
            Return False
        End If
    Next
    Return True
End Function

Answer 6

Pointless Haskell version (15 chars, though doesn't really work unless you include Control.Arrow and Control.Monad and ignore the monomorphism restriction):

p=ap(==)reverse