first commit

Author: Hawstein

README.md

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+## Snake AI
+
+A snake AI written in python. Use curses module, Windows users 
+should install it first:
+
+<http://www.lfd.uci.edu/~gohlke/pythonlibs/#curses>
+
+
+## How to run
+
+	git clone https://github.com/Hawstein/snake-ai.git
+	cd snake-ai
+	python snake.py
+	
+## Demo
+
+<img src="snake-ai.gif" />

snake-ai.gif

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+# coding: utf-8
+
+import curses
+from curses import KEY_RIGHT, KEY_LEFT, KEY_UP, KEY_DOWN
+from random import randint
+
+# 蛇运动的场地长宽
+HEIGHT = 10
+WIDTH = 20
+FIELD_SIZE = HEIGHT * WIDTH
+
+# 蛇头总是位于snake数组的第一个元素
+HEAD = 0
+
+# 用来代表不同东西的数字，由于矩阵上每个格子会处理成到达食物的路径长度，
+# 因此这三个变量间需要有足够大的间隔(>HEIGHT*WIDTH)
+FOOD = 0
+UNDEFINED = (HEIGHT + 1) * (WIDTH + 1)
+SNAKE = 2 * UNDEFINED
+
+# 由于snake是一维数组，所以对应元素直接加上以下值就表示向四个方向移动
+LEFT = -1
+RIGHT = 1
+UP = -WIDTH
+DOWN = WIDTH
+
+# 错误码
+ERR = -1111
+
+# 用一维数组来表示二维的东西
+# board表示蛇运动的矩形场地
+# 初始化蛇头在(1,1)的地方，第0行，HEIGHT行，第0列，WIDTH列为围墙，不可用
+# 初始蛇长度为1
+board = [0] * FIELD_SIZE
+snake = [0] * (FIELD_SIZE+1)
+snake[HEAD] = 1*WIDTH+1
+snake_size = 1
+# 与上面变量对应的临时变量，蛇试探性地移动时使用
+tmpboard = [0] * FIELD_SIZE
+tmpsnake = [0] * (FIELD_SIZE+1)
+tmpsnake[HEAD] = 1*WIDTH+1
+tmpsnake_size = 1
+
+# food:食物位置(0~FIELD_SIZE-1),初始在(3, 3)
+# best_move: 运动方向
+food = 3 * WIDTH + 3
+best_move = ERR
+
+# 运动方向数组
+mov = [LEFT, RIGHT, UP, DOWN]
+# 接收到的键 和 分数
+key = KEY_RIGHT                                                    
+score = 1 #分数也表示蛇长
+
+# 检查一个cell有没有被蛇身覆盖，没有覆盖则为free，返回true
+def is_cell_free(idx, psize, psnake):
+    #return not (idx in psnake[:]) #错！psnake后面还有很多没用上的单元
+    for i in xrange(psize):
+        if idx == psnake[i]: return False
+    return True
+    
+
+# 检查某个位置idx是否可向move方向运动
+def is_move_possible(idx, move):
+    flag = False
+    if move == LEFT:
+        flag = True if idx%WIDTH > 1 else False
+    elif move == RIGHT:
+        flag = True if idx%WIDTH < (WIDTH-2) else False
+    elif move == UP:
+        flag = True if idx > (2*WIDTH-1) else False # 即idx/WIDTH > 1
+    elif move == DOWN:
+        flag = True if idx < (FIELD_SIZE-2*WIDTH) else False # 即idx/WIDTH < HEIGHT-2
+    return flag
+# 重置board
+# board_refresh后，UNDEFINED值都变为了到达食物的路径长度
+# 如需要还原，则要重置它
+def board_reset(psnake, psize, pboard):
+    for i in xrange(FIELD_SIZE):
+       # f.write('hello ' + str(len(pboard)) +' ' +str(i)+'\n')
+        if i == food:
+            pboard[i] = FOOD
+        elif is_cell_free(i, psize, psnake): # 该位置为空
+            pboard[i] = UNDEFINED
+        else: # 该位置为蛇身
+            pboard[i] = SNAKE
+    
+# def board_refresh(pfood, psnake, pboard):
+#     board_changed = True
+#     found = False
+#     while board_changed: # 一直更新board，直到每个格子上的数都对应到达食物的步数，不能再改变为止
+#         board_changed = False
+#         for i in xrange(FIELD_SIZE):
+#             if pboard[i] < SNAKE: 
+#                 min = pboard[i]
+#                 for j in xrange(4):
+#                     if is_move_possible(i, mov[j]) and pboard[i+mov[j]] < min:
+#                         min = pboard[i+mov[j]]
+#                 if pboard[i] > min+1:
+#                     pboard[i] = min + 1
+#                     board_changed = True
+
+#         if ~board_changed: break # 不再改变，退出
+#         board_changed = False
+
+#         for i in xrange(FIELD_SIZE-1, -1, -1): # [FIELD_SIZE-1, 0]
+#             if pboard[i] < SNAKE:
+#                 min = pboard[i]
+#                 for j in xrange(4):
+#                     if is_move_possible(i, mov[j]) and pboard[i+mov[j]] < min:
+#                         min = pboard[i+mov[j]]
+#                 if pboard[i] > min+1:
+#                     pboard[i] = min + 1
+#                     board_changed = True
+#     for i in xrange(4):
+#         if is_move_possible(psnake[HEAD], mov[i]) and pboard[psnake[HEAD]+mov[i]]<UNDEFINED:
+#             flag = True
+
+#     return flag
+
+# 广度优先搜索遍历整个board，
+# 计算出board中每个非SNAKE元素到达食物的路径长度
+def board_refresh(pfood, psnake, pboard):
+    queue = []
+    queue.append(pfood)
+    inqueue = [0] * FIELD_SIZE
+    found = False
+    # while循环结束后，除了蛇的身体，
+    # 其它每个方格中的数字代码从它到食物的路径长度
+    #f.write('bfs begin:\n')
+    while len(queue)!=0: 
+        idx = queue.pop(0)
+        if inqueue[idx] == 1: continue
+        #f.write(str(idx)+'\n')
+        inqueue[idx] = 1
+        for i in xrange(4):
+            if is_move_possible(idx, mov[i]):
+                if idx + mov[i] == psnake[HEAD]:
+                    found = True
+                if pboard[idx+mov[i]] < SNAKE: # 如果该点不是蛇的身体
+                    
+                    if pboard[idx+mov[i]] > pboard[idx]+1:
+                        pboard[idx+mov[i]] = pboard[idx] + 1
+                    if inqueue[idx+mov[i]] == 0:
+                        queue.append(idx+mov[i])
+
+    #f.write('bfs end\n')
+    #f.write('found: ' + str(found) +'\n')
+    return found
+
+# 从蛇头开始，根据board中元素值，
+# 从蛇头周围4个领域点中选择最短路径
+def choose_shortest_safe_move(psnake, pboard):
+    best_move = ERR
+    min = SNAKE
+    for i in xrange(4):
+        if is_move_possible(psnake[HEAD], mov[i]) and pboard[psnake[HEAD]+mov[i]]<min:
+            min = pboard[psnake[HEAD]+mov[i]]
+            best_move = mov[i]
+    return best_move
+
+# 从蛇头开始，根据board中元素值，
+# 从蛇头周围4个领域点中选择最远路径
+def choose_longest_safe_move(psnake, pboard):
+    best_move = ERR
+    max = -1
+    for i in xrange(4):
+        if is_move_possible(psnake[HEAD], mov[i]) and pboard[psnake[HEAD]+mov[i]]<UNDEFINED and pboard[psnake[HEAD]+mov[i]]>max:
+            max = pboard[psnake[HEAD]+mov[i]]
+            best_move = mov[i]
+    return best_move
+
+# 检查是否可以追着蛇尾运动，即蛇头和蛇尾间是有路径的
+# 为的是避免蛇头陷入死路
+# 虚拟操作，在tmpboard,tmpsnake中进行
+def is_tail_inside():
+    global tmpboard, tmpsnake, food, tmpsnake_size
+    tmpboard[tmpsnake[tmpsnake_size-1]] = 0 # 虚拟地将蛇尾变为食物(因为是虚拟的，所以在tmpsnake,tmpboard中进行)
+    tmpboard[food] = SNAKE # 放置食物的地方，看成蛇身
+    result = board_refresh(tmpsnake[tmpsnake_size-1], tmpsnake, tmpboard) # 求得每个位置到蛇尾的路径长度
+    for i in xrange(4): # 如果蛇头和蛇尾紧挨着，则返回False。即不能follow_tail，追着蛇尾运动了
+        if is_move_possible(tmpsnake[HEAD], mov[i]) and tmpsnake[HEAD]+mov[i]==tmpsnake[tmpsnake_size-1] and tmpsnake_size>3:
+            result = False
+    return result
+
+# 让蛇头朝着蛇尾运行一步
+# 不管蛇身阻挡，朝蛇尾方向运行
+def follow_tail():
+    global tmpboard, tmpsnake, food, tmpsnake_size
+    tmpsnake_size = snake_size
+    tmpsnake = snake[:]
+    board_reset(tmpsnake, tmpsnake_size, tmpboard) # 重置虚拟board
+    tmpboard[tmpsnake[tmpsnake_size-1]] = FOOD # 让蛇尾成为食物
+    tmpboard[food] = SNAKE # 让食物的地方变成蛇身
+    board_refresh(tmpsnake[tmpsnake_size-1], tmpsnake, tmpboard) # 求得各个位置到达蛇尾的路径长度
+    tmpboard[tmpsnake[tmpsnake_size-1]] = SNAKE # 还原蛇尾
+
+    # return choose_longest_safe_move(tmpsnake, tmpboard) # 返回运行方向(让蛇头运动1步)
+    return choose_longest_safe_move(tmpsnake, tmpboard)
+
+# 在各种方案都不行时，随便找一个可行的方向来走(1步),
+def any_possible_move():
+    global food , snake, snake_size, board
+    best_move = ERR
+    board_reset(snake, snake_size, board)
+    board_refresh(food, snake, board)
+    min = SNAKE
+
+    for i in xrange(4):
+        if is_move_possible(snake[HEAD], mov[i]) and board[snake[HEAD]+mov[i]]<min:
+            min = board[snake[HEAD]+mov[i]]
+            best_move = mov[i]
+    return best_move
+
+def shift_array(arr, size):
+    for i in xrange(size, 0, -1):
+        arr[i] = arr[i-1]
+
+def new_food():
+    global food, snake_size
+    if snake_size >= FIELD_SIZE-1: return
+    cell_free = False
+    while not cell_free:
+        w = randint(1, WIDTH-2)
+        h = randint(1, HEIGHT-2)
+        food = h * WIDTH + w
+        cell_free = is_cell_free(food, snake_size, snake)
+    win.addch(food/WIDTH, food%WIDTH, '@')
+
+# 真正的蛇在这个函数中，朝pbest_move走1步
+def make_move(pbest_move):
+    global key, snake, board, snake_size, score
+    shift_array(snake, snake_size)
+    snake[HEAD] += pbest_move
+    
+
+    # 按esc退出，getch同时保证绘图的流畅性，没有它只会看到最终结果
+    win.timeout(10)
+    event = win.getch()
+    key = key if event == -1 else event
+    if key == 27: return
+
+    p = snake[HEAD]
+    win.addch(p/WIDTH, p%WIDTH, '*')
+
+    
+    # 如果新加入的蛇头就是食物的位置
+    # 蛇长加1，产生新的食物，重置board(因为原来那些路径长度已经用不上了)
+    if snake[HEAD] == food:
+        board[snake[HEAD]] = SNAKE # 新的蛇头
+        snake_size += 1
+        score += 1
+        if snake_size < FIELD_SIZE: new_food()
+        #board_reset(snake, board) # 
+        #return True
+    else: # 如果新加入的蛇头不是食物的位置
+        board[snake[HEAD]] = SNAKE # 新的蛇头
+        board[snake[snake_size]] = UNDEFINED # 蛇尾变为空格
+        win.addch(snake[snake_size]/WIDTH, snake[snake_size]%WIDTH, ' ')
+        #return False
+    # test 打印tmpboard
+    for i in xrange(HEIGHT):
+        for j in xrange(WIDTH):
+            k = board[i*WIDTH+j]
+            f.write(str(k)+' ')
+        f.write('\n')
+    # print symbol
+    for i in xrange(HEIGHT):
+        for j in xrange(WIDTH):
+            k = board[i*WIDTH+j]
+            if k == UNDEFINED:
+                f.write('# ')
+            elif k == SNAKE:
+                if i*WIDTH+j == snake[HEAD]:
+                    f.write('+ ') # 蛇头
+                elif i*WIDTH+j == snake[snake_size-1]:
+                    f.write('- ') # 蛇尾
+                else:
+                    f.write('* ')
+            else:
+                f.write(str(k)+' ')
+        f.write('\n')
+    f.write('\n')
+
+# 虚拟地运行一次，然后在调用处检查这次运行可否可行
+# 可行才真实运行。
+# 虚拟运行吃到食物后，得到虚拟下蛇在board的位置
+def virtual_shortest_move():
+    global snake, board, snake_size, tmpsnake, tmpboard, tmpsnake_size, food
+    #f.write('i am in virtual\n')
+    tmpsnake_size = snake_size
+    tmpsnake = snake[:] # 如果直接tmpsnake=snake，则两者指向同一处内存
+    tmpboard = board[:] # board中已经是各位置到达食物的路径长度了，不用再计算
+    board_reset(tmpsnake, tmpsnake_size, tmpboard)
+    
+
+    # test 打印tmpboard
+    # for i in xrange(HEIGHT):
+    #     for j in xrange(WIDTH):
+    #         k = tmpboard[i*WIDTH+j]
+    #         f.write(str(k)+' ')
+    #     f.write('\n')
+    
+    food_eated = False
+    while not food_eated:
+        board_refresh(food, tmpsnake, tmpboard)    
+        move = choose_shortest_safe_move(tmpsnake, tmpboard)
+        shift_array(tmpsnake, tmpsnake_size)
+        tmpsnake[HEAD] += move # 在蛇头前加入一个新的位置
+        #f.write('snake head: '+str(tmpsnake[HEAD])+'\n')
+        # 如果新加入的蛇头的位置正好是食物的位置
+        # 则长度加1，重置board，食物那个位置变为蛇的一部分(SNAKE)
+        if tmpsnake[HEAD] == food:
+            tmpsnake_size += 1
+            board_reset(tmpsnake, tmpsnake_size, tmpboard) # 虚拟运行后，蛇在board的位置(label101010)
+            tmpboard[food] = SNAKE
+            food_eated = True
+        else: # 如果蛇头不是食物的位置，则新加入的位置为蛇头，最后一个变为空格
+            tmpboard[tmpsnake[HEAD]] = SNAKE
+            tmpboard[tmpsnake[tmpsnake_size]] = UNDEFINED
+    #f.write('i am out virtual\n')
+
+# 如果蛇与食物间有路径，则调用本函数
+def find_safe_way():
+    global snake, board
+    safe_move = ERR
+    # 虚拟地运行一次，因为已经确保蛇与食物间有路径，所以执行有效
+    # 运行后得到虚拟下蛇在board中的位置，即tmpboard，见label101010
+    virtual_shortest_move() # 该函数唯一调用处
+    if is_tail_inside(): # 如果虚拟运行后，蛇头蛇尾间有通路，则选最短路运行(1步)
+        return choose_shortest_safe_move(snake, board)
+    safe_move = follow_tail() # 否则虚拟地follow_tail 1步，如果可以做到，返回true
+    return safe_move
+
+
+curses.initscr()
+win = curses.newwin(HEIGHT, WIDTH, 0, 0)
+win.keypad(1)
+curses.noecho()
+curses.curs_set(0)
+win.border(0)
+win.nodelay(1)
+win.addch(food/WIDTH, food%WIDTH, '@')
+
+f = file('log', 'w')
+    
+while key != 27:
+    win.border(0)
+    win.addstr(0, 2, 's:' + str(score) + ' ')               
+    #win.addstr(0, WIDTH/2-3, ' SNAKE ')                                  
+    win.timeout(10)
+    # 接收键盘输入，同时也使显示流畅
+    event = win.getch()
+    key = key if event == -1 else event
+    if snake_size >= FIELD_SIZE: continue
+    # 重置矩阵
+    board_reset(snake, snake_size, board)
+    
+    # 如果蛇可以吃到食物，board_refresh返回true
+    # 并且board中除了蛇身(=SNAKE)，其它的元素值表示从该点运动到食物的最短路径长
+    if board_refresh(food, snake, board):
+        best_move  = find_safe_way() # find_safe_way的唯一调用处
+        f.write('find safe way: ' + str(best_move) + '\n')
+    else:
+        best_move = follow_tail()
+        f.write('follow tail: ' + str(best_move) +'\n')
+            
+    if best_move == ERR:
+        best_move = any_possible_move()
+        f.write('any possible move: ' + str(best_move) + '\n')
+    # 上面一次思考，只得出一个方向，运行一步
+    if best_move != ERR: make_move(best_move)   
+    else: break        
+        
+f.close()
+curses.endwin()
+print("\nScore - " + str(score))
+