Code Golf: Tic Tac Toe

Answer 1

Lua, 130 characters

The 130 characters is the function size only. The function returns nothing if no match is found, which in Lua is similar to returning false.

function f(t)z={7,1,4,1,1,3,2,3,3}for b=1,#z-1 do
i=z[b]x=t[i]n=z[b+1]if 0<x and x==t[i+n]and x==t[i+n+n]then
return x end end end

assert(f{1,2,1,0,1,2,1,0,2}==1)
assert(f{1,2,1,0,0,2,1,0,2}==nil)
assert(f{1,1,2,0,1,2,1,0,2}==2)
assert(f{2,1,2,1,2,1,2,1,2}==2)
assert(f{2,1,2,1,0,2,2,2,1}==nil)
assert(f{1,2,0,1,2,0,1,2,0}~=nil)
assert(f{0,2,0,0,2,0,0,2,0}==2)
assert(f{0,2,2,0,0,0,0,2,0}==nil)

assert(f{0,0,0,0,0,0,0,0,0}==nil)
assert(f{1,1,1,0,0,0,0,0,0}==1)
assert(f{0,0,0,1,1,1,0,0,0}==1)
assert(f{0,0,0,0,0,0,1,1,1}==1)
assert(f{1,0,0,1,0,0,1,0,0}==1)
assert(f{0,1,0,0,1,0,0,1,0}==1)
assert(f{0,0,1,0,0,1,0,0,1}==1)
assert(f{1,0,0,0,1,0,0,0,1}==1)
assert(f{0,0,1,0,1,0,1,0,0}==1)

Answer 2

Python, 140 chars

My first code golf, weighing in at a hefty 140 chars (import statement, I deny you!):

import operator as o

def c(t):return({1:1,8:2}.get(reduce(o.mul,t[:3]),0))
def g(t):return max([c(t[x::y]) for x,y in zip((0,0,0,1,2,2,3,6),(1,3,4,3,3,2,1,1))])

Slightly less obscure g:

def g(t):return max([c(t[x::y]) for x,y in [[0,1],[0,3],[0,4],[1,3],[2,3],[2,2],[3,1],[6,1]]])

Answer 3

C, 77 (83) characters

This is a variant of dmckee's solution, except that each pair of digits in the Compact Coding is now the base-9 digits of the ASCII characters.

The 77-char version, does not work on MSVC:

// "J)9\t8\r=,\0" == 82,45,63,10,62,14,67,48,00 in base 9.
char*k="J)9 8\r=,",c;f(int*b){return(c=*k++)?b[c/9]&b[c%9]&b[*k--%9]|f(b):0;}

This 83-char version, should work on every C compiler:

f(int*b){char*k="J)9    8\r=,",s=0,c;while(c=*k++)s|=b[c%9]&b[c/9]&b[*k%9];return s;}

(Note that the spaces between the 9 and 8 should be a tab. StackOverflow converts all tabs into spaces.)

---

Test case:

#include <stdio.h>  
void check(int* b) {
    int h0 = b[0]&b[1]&b[2];
    int h1 = b[3]&b[4]&b[5];
    int h2 = b[6]&b[7]&b[8];
    int h3 = b[0]&b[3]&b[6];
    int h4 = b[1]&b[4]&b[7];
    int h5 = b[2]&b[5]&b[8];
    int h6 = b[0]&b[4]&b[8];
    int h7 = b[2]&b[4]&b[6];
    int res = h0|h1|h2|h3|h4|h5|h6|h7;
    int value = f(b);
    if (value != res)
        printf("Assuming f({%d,%d,%d, %d,%d,%d, %d,%d,%d}) == %d; got %d instead.\n", 
            b[0],b[1],b[2], b[3],b[4],b[5], b[6],b[7],b[8], res, value);
}
#define MAKEFOR(i) for(b[(i)]=0;b[(i)]<=2;++b[(i)])

int main() {
    int b[9];

    MAKEFOR(0)
    MAKEFOR(1)
    MAKEFOR(2)
    MAKEFOR(3)
    MAKEFOR(4)
    MAKEFOR(5)
    MAKEFOR(6)
    MAKEFOR(7)
    MAKEFOR(8)
        check(b);

    return 0;
}

Answer 4

J, 50 chars

w=:3 : '{.>:I.+./"1*./"1]1 2=/y{~2 4 6,0 4 8,i,|:i=.i.3 3'

Answer 5

(Iron)python, 75 characters

75 characters for a full function

T=lambda a:max(a[b/6]&a[b/6+b%6]&a[b/6+b%6*2]for b in[1,3,4,9,14,15,19,37])

66 characters if you leave out the function definition like some others have done

r=max(a[b/6]&a[b/6+b%6]&a[b/6+b%6*2]for b in[1,3,4,9,14,15,19,37])

The 8 different directions are represented by starting value + incrementor, compressed into a single number that can be extracted using division and modula. For example 2,5,8 = 2*6 + 3 = 15.

Checking that a row contains three equal values is done using the & operator. (which results in zero if they aren't equal). max is used to find the possible winner.

Answer 6

c -- 144 characters

Minified:

#define A(x) a[b[x%16]]
int c,b[]={4,8,0,1,2,4,6,0,3,4,5,2,8,6,7,2};int
T(int*a){for(c=0;c<16;c+=2)if(A(c)&A(c+1)&A(c+2))return A(c);return 0;}

Both returns count (one necessary and the other would need replacing with a space).

The array codes for the eight ways to win in triplets starting from even positions and taken mod 16.

Bitwise and trick stolen from Eric Pi.

---

More readable form:

#define A(x) a[b[x%16]]

// Compact coding of the ways to win.
//
// Each possible was starts a position N*2 and runs through N*2+2 all
// taken mod 16
int c,b[]={4,8,0,1,2,4,6,0,3,4,5,2,8,6,7,2};

int T(int*a){
  // Loop over the ways to win
  for(c=0;c<16;c+=2)
    // Test for a win
    if(A(c)&A(c+1)&A(c+2))return A(c);
  return 0;
}

Testing scaffold:

#include <stdlib.h>
#include <stdio.h>

int T(int*);

int main(int argc, char**argv){
  int input[9]={0};
  int i, j;
  for (i=1; i<argc; ++i){
    input[i-1] = atoi(argv[i]);
  };
  for (i=0;i<3;++i){
    printf("%1i  %1i  %1i\n",input[3*i+0],input[3*i+1],input[3*i+2]);
  };
  if (i = T(input)){
    printf("%c wins!\n",(i==1)?'X':'O');
  } else {
    printf("No winner.\n");
  }
  return 0;
}