Code Golf: Tic Tac Toe

Answer 1

Ruby, 115 chars

Oops: Somehow I miscounted by a lot. This is actually 115 characters, not 79.

def t(b)[1,2].find{|p|[448,56,7,292,146,73,273,84].any?{|k|(k^b.inject(0){|m,i|m*2+((i==p)?1:0)})&k==0}}||false end

# Usage:
b = [ 1, 2, 1,
      0, 1, 2,
      1, 0, 2 ]
t(b) # => 1

b = [ 1, 1, 0,
      2, 2, 2,
      0, 2, 1 ]
t(b) # => 2

b = [ 0, 0, 1,
      2, 2, 0,
      0, 1, 1 ]
t(b) # => false

And the expanded code, for educational purposes:

def tic(board)
  # all the winning board positions for a player as bitmasks
  wins = [ 0b111_000_000,  # 448
           0b000_111_000,  #  56
           0b000_000_111,  #   7
           0b100_100_100,  # 292
           0b010_010_010,  # 146
           0b001_001_001,  #  73
           0b100_010_001,  # 273
           0b001_010_100 ] #  84

  [1, 2].find do |player| # find the player who's won
    # for the winning player, one of the win positions will be true for :
    wins.any? do |win|
      # make a bitmask from the current player's moves
      moves = board.inject(0) { |acc, square|
        # shift it to the left and add one if this square matches the player number
        (acc * 2) + ((square == player) ? 1 : 0)
      }
      # some logic evaluates to 0 if the moves match the win mask
      (win ^ moves) & win == 0
    end
  end || false # return false if the find returns nil (no winner)
end

I'm sure this could be shortened, especially the big array and possibly the code for getting a bitmask of the players's moves--that ternary bugs me--but I think this is pretty good for now.

Answer 2

A solution in C (162 Characters):

This makes use of the fact that player one value (1) and player two value (2) have independent bits set. Therefore, you can bitwise AND the values of the three test boxes together-- if the value is nonzero, then all three values must be identical. In addition, the resulting value == the player that won.

Not the shortest solution so far, but the best I could do:

void fn(){
    int L[]={1,0,1,3,1,6,3,0,3,1,3,2,4,0,2,2,0};
    int s,t,p,j,i=0;
    while (s=L[i++]){
        p=L[i++],t=3;
        for(j=0;j<3;p+=s,j++)t&=b[p];
        if(t)putc(t+'0',stdout);}
}

A more readable version:

void fn2(void)
{
    // Lines[] defines the 8 lines that must be tested
    //  The first value is the "Skip Count" for forming the line
    //  The second value is the starting position for the line
    int Lines[] = { 1,0, 1,3, 1,6, 3,0, 3,1, 3,2, 4,0, 2,2, 0 };

    int Skip, Test, Pos, j, i = 0;
    while (Skip = Lines[i++])
    {
        Pos = Lines[i++];   // get starting position
        Test = 3;           // pre-set to 0x03 (player 1 & 2 values bitwise OR'd together)

        // search each of the three boxes in this line
        for (j = 0; j < 3; Pos+= Skip, j++)
        {
            // Bitwise AND the square with the previous value
            //  We make use of the fact that player 1 is 0x01 and 2 is 0x02
            //  Therefore, if any bits are set in the result, it must be all 1's or all 2's
            Test &= b[Pos];
        }

        // All three squares same (and non-zero)?
        if (Test)
            putc(Test+'0',stdout);
    }
}

Answer 3

C#, 180 characters :

var s=new[]{0,0,0,1,2,2,3,6};
var t=new[]{1,3,4,3,2,3,1,1};
return(s.Select((p,i)=>new[]{g[p],g[p+t[i]],g[p+2*t[i]]}).FirstOrDefault(l=>l.Distinct().Count()==1)??new[]{0}).First();

(g being the grid)

Could probably be improved... I'm still working on it ;)

Answer 4

Python, 102 characters

Since you didn't really specify how to get input and output, this is the "raw" version that would perhaps have to be wrapped into a function. b is the input list; r is the output (0, 1 or 2).

r=0
for a,c in zip("03601202","11133342"):s=set(b[int(a):9:int(c)][:3]);q=s.pop();r=r if s or r else q

Answer 5

Probably could be made better, but I'm not feeling particularly clever right now. This is just to make sure Haskell gets represented...

Assuming that b already exists, this will put the result in w.

import List
a l=2*minimum l-maximum l
z=take 3$unfoldr(Just .splitAt 3)b
w=maximum$0:map a(z++transpose z++[map(b!!)[0,4,8],map(b!!)[2,4,6]])

Assuming input from stdin and output to stdout,

import List
a l=2*minimum l-maximum l
w b=maximum$0:map a(z++transpose z++[map(b!!)[0,4,8],map(b!!)[2,4,6]])where
 z=take 3$unfoldr(Just .splitAt 3)b
main=interact$show.w.read

Answer 6

Crazy Python solution - 79 characters

max([b[x] for x in range(9) for y in range(x) for z in range(y)
    if x+y+z==12 and b[x]==b[y]==b[z]] + [0])

However, this assumes a different order for the board positions in b:

 5 | 0 | 7
---+---+---
 6 | 4 | 2
---+---+---
 1 | 8 | 3

That is, b[5] represents the top-left corner, and so on.

To minimize the above:

r=range
max([b[x]for x in r(9)for y in r(x)for z in r(y)if x+y+z==12and b[x]==b[y]==b[z]]+[0])

93 characters and a newline.

Update: Down to 79 characters and a newline using the bitwise AND trick:

r=range
max([b[x]&b[y]&b[z]for x in r(9)for y in r(x)for z in r(y)if x+y+z==12])