2048(http://gabrielecirulli.github.io/2048/ )のAI。JavaScriptの方はゲーム画面からゲーム状態を取り出してAIの呼出しコードに変換するブックマークレット。

2048-ai.py

DIR_UP = 0
DIR_DOWN = 1
DIR_RIGHT = 2
DIR_LEFT = 3
DIR_SENTINEL = 4

WIDTH = 4
HEIGHT = 4

def make_board():
  return [[0 for i in range(WIDTH)] for j in range(HEIGHT)]

def copy_board(board):
  return [[elm for elm in row] for row in board]

def update(board, direction):
  new_board = make_board()
  dx = [0, 0, -1, 1][direction]
  dy = [1, -1, 0, 0][direction]
  x = [0, 0, WIDTH-1, 0][direction]
  y = [0, HEIGHT-1, 0, 0][direction]
  for i in range(WIDTH):
    to_x = x
    to_y = y
    can_merge = False
    for j in range(HEIGHT):
      if board[y][x] == 0:
        pass
      elif can_merge and 0 <= to_y-dy < HEIGHT and 0 <= to_x-dx < WIDTH and board[y][x] == new_board[to_y-dy][to_x-dx]:
        new_board[to_y-dy][to_x-dx] = board[y][x] * 2
        can_merge = False
      else:
        new_board[to_y][to_x] = board[y][x]
        to_x += dx
        to_y += dy
        can_merge = True
      x += dx
      y += dy
    x = [x+1, x+1, WIDTH-1, 0][direction]
    y = [0, HEIGHT-1, y+1, y+1][direction]
  return new_board

def same(board_a, board_b):
  for i in range(HEIGHT):
    for j in range(WIDTH):
      if board_a[i][j] != board_b[i][j]:
        return False
  return True

def is_gameover(board):
  return same(board, update(board, DIR_UP)) and same(board, update(board, DIR_RIGHT))

EVAL_MIN = -100000000
def evaluate(board):
  if is_gameover(board):
    return EVAL_MIN
  num_zero = 0
  for row in board:
    for elm in row:
      if elm == 0:
        num_zero += 1
  #max_ = max([max(row) for row in board])
  sum_ = sum([sum(row) for row in board])
  return sum_/(WIDTH*HEIGHT-num_zero)**2

TURN_PLAYER = 0
TURN_MASTER = 1
def minimax(board, turn, depth):
  if depth == 0 or is_gameover(board):
    return evaluate(board)
  res = []
  if turn == TURN_PLAYER:
    for choice in range(DIR_SENTINEL):
      if not(same(board, update(board, choice))):
        res.append(minimax(update(board, choice), TURN_MASTER, depth-1))
    return max(res)
  elif turn == TURN_MASTER:
    for i in range(HEIGHT):
      for j in range(WIDTH):
        if board[i][j] == 0:
          new_board = copy_board(board)
          new_board[i][j] = 2 # Actually, 2 and 4 can be put, but I ignored case of 4...
          res.append(minimax(new_board, TURN_PLAYER, depth-1))
    return min(res)

def ai_choice(board):
  res_max = EVAL_MIN
  choice_max = DIR_SENTINEL
  for choice in range(DIR_SENTINEL):
    if not(same(board, update(board, choice))):
      res = minimax(update(board, choice), TURN_MASTER, 4)
      if res > res_max:
        res_max = res
        choice_max = choice
  print(res_max)
  return choice_max

#utility
def str_to_board(s):
  ss = s.split(",")
  board = make_board()
  for i in range(HEIGHT):
    for j in range(WIDTH):
      board[i][j] = int(ss[i*WIDTH+j])
  return board
def dir_to_name(direction):
  return [ "DIR_UP", "DIR_DOWN", "DIR_RIGHT", "DIR_LEFT"][direction]
def show_board(board):
  for i in range(HEIGHT):
    print(board[i])

get-game-state.js

(function(){
var board = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0];
for(var y=0;y<4;y++){
  for(var x=0;x<4;x++){
    var elm = document.querySelectorAll(".tile-position-"+(x+1)+"-"+(y+1));
    if(elm.length>1){
      var elm = document.querySelector(".tile-position-"+(x+1)+"-"+(y+1)+".tile-merged");
      board[y*4+x] = elm.textContent - 0;
    }else if(elm.length==1){
      board[y*4+x] = elm[0].textContent - 0;
    }
  }
}
alert('dir_to_name(ai_choice(str_to_board("'+board.join()+'")))')
})()

//javascript:(function(){ var board = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]; for(var y=0;y<4;y++){ for(var x=0;x<4;x++){ var elm = document.querySelectorAll(".tile-position-"+(x+1)+"-"+(y+1)); if(elm.length>1){ var elm = document.querySelector(".tile-position-"+(x+1)+"-"+(y+1)+".tile-merged"); board[y*4+x] = elm.textContent - 0; }else if(elm.length==1){ board[y*4+x] = elm[0].textContent - 0; } } } alert('dir_to_name(ai_choice(str_to_board("'+board.join()+'")))') })()