用Python寫一個貪吃蛇AI
阿新 • • 發佈:2019-02-16
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# coding: utf-8 import curses from curses import KEY_RIGHT, KEY_LEFT, KEY_UP, KEY_DOWN from random import randint # 蛇運動的場地長寬 HEIGHT = 10 WIDTH = 20 FIELD_SIZE = HEIGHT * WIDTH # 蛇頭總是位於snake陣列的第一個元素 HEAD = 0 # 用來代表不同東西的數字,由於矩陣上每個格子會處理成到達食物的路徑長度, # 因此這三個變數間需要有足夠大的間隔(>HEIGHT*WIDTH) FOOD = 0 UNDEFINED = (HEIGHT + 1) * (WIDTH + 1) SNAKE = 2 * UNDEFINED # 由於snake是一維陣列,所以對應元素直接加上以下值就表示向四個方向移動 LEFT = -1 RIGHT = 1 UP = -WIDTH DOWN = WIDTH # 錯誤碼 ERR = -1111 # 用一維陣列來表示二維的東西 # board表示蛇運動的矩形場地 # 初始化蛇頭在(1,1)的地方,第0行,HEIGHT行,第0列,WIDTH列為圍牆,不可用 # 初始蛇長度為1 board = [0] * FIELD_SIZE snake = [0] * (FIELD_SIZE+1) snake[HEAD] = 1*WIDTH+1 snake_size = 1 # 與上面變數對應的臨時變數,蛇試探性地移動時使用 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: 運動方向 food = 3 * WIDTH + 3 best_move = ERR # 運動方向陣列 mov = [LEFT, RIGHT, UP, DOWN] # 接收到的鍵 和 分數 key = KEY_RIGHT score = 1 #分數也表示蛇長 # 檢查一個cell有沒有被蛇身覆蓋,沒有覆蓋則為free,返回true def is_cell_free(idx, psize, psnake): return not (idx in psnake[:psize]) # 檢查某個位置idx是否可向move方向運動 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後,UNDEFINED值都變為了到達食物的路徑長度 # 如需要還原,則要重置它 def board_reset(psnake, psize, pboard): for i in xrange(FIELD_SIZE): if i == food: pboard[i] = FOOD elif is_cell_free(i, psize, psnake): # 該位置為空 pboard[i] = UNDEFINED else: # 該位置為蛇身 pboard[i] = SNAKE # 廣度優先搜尋遍歷整個board, # 計算出board中每個非SNAKE元素到達食物的路徑長度 def board_refresh(pfood, psnake, pboard): queue = [] queue.append(pfood) inqueue = [0] * FIELD_SIZE found = False # while迴圈結束後,除了蛇的身體, # 其它每個方格中的數字程式碼從它到食物的路徑長度 while len(queue)!=0: idx = queue.pop(0) if inqueue[idx] == 1: continue 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: # 如果該點不是蛇的身體 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]) return found # 從蛇頭開始,根據board中元素值, # 從蛇頭周圍4個領域點中選擇最短路徑 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 # 從蛇頭開始,根據board中元素值, # 從蛇頭周圍4個領域點中選擇最遠路徑 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 # 檢查是否可以追著蛇尾運動,即蛇頭和蛇尾間是有路徑的 # 為的是避免蛇頭陷入死路 # 虛擬操作,在tmpboard,tmpsnake中進行 def is_tail_inside(): global tmpboard, tmpsnake, food, tmpsnake_size tmpboard[tmpsnake[tmpsnake_size-1]] = 0 # 虛擬地將蛇尾變為食物(因為是虛擬的,所以在tmpsnake,tmpboard中進行) tmpboard[food] = SNAKE # 放置食物的地方,看成蛇身 result = board_refresh(tmpsnake[tmpsnake_size-1], tmpsnake, tmpboard) # 求得每個位置到蛇尾的路徑長度 for i in xrange(4): # 如果蛇頭和蛇尾緊挨著,則返回False。即不能follow_tail,追著蛇尾運動了 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 # 讓蛇頭朝著蛇尾執行一步 # 不管蛇身阻擋,朝蛇尾方向執行 def follow_tail(): global tmpboard, tmpsnake, food, tmpsnake_size tmpsnake_size = snake_size tmpsnake = snake[:] board_reset(tmpsnake, tmpsnake_size, tmpboard) # 重置虛擬board tmpboard[tmpsnake[tmpsnake_size-1]] = FOOD # 讓蛇尾成為食物 tmpboard[food] = SNAKE # 讓食物的地方變成蛇身 board_refresh(tmpsnake[tmpsnake_size-1], tmpsnake, tmpboard) # 求得各個位置到達蛇尾的路徑長度 tmpboard[tmpsnake[tmpsnake_size-1]] = SNAKE # 還原蛇尾 return choose_longest_safe_move(tmpsnake, tmpboard) # 返回執行方向(讓蛇頭運動1步) # 在各種方案都不行時,隨便找一個可行的方向來走(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 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, '@') # 真正的蛇在這個函式中,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同時保證繪圖的流暢性,沒有它只會看到最終結果 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, '*') # 如果新加入的蛇頭就是食物的位置 # 蛇長加1,產生新的食物,重置board(因為原來那些路徑長度已經用不上了) if snake[HEAD] == food: board[snake[HEAD]] = SNAKE # 新的蛇頭 snake_size += 1 score += 1 if snake_size < FIELD_SIZE: new_food() else: # 如果新加入的蛇頭不是食物的位置 board[snake[HEAD]] = SNAKE # 新的蛇頭 board[snake[snake_size]] = UNDEFINED # 蛇尾變為空格 win.addch(snake[snake_size]/WIDTH, snake[snake_size]%WIDTH, ' ') # 虛擬地執行一次,然後在呼叫處檢查這次執行可否可行 # 可行才真實執行。 # 虛擬執行吃到食物後,得到虛擬下蛇在board的位置 def virtual_shortest_move(): global snake, board, snake_size, tmpsnake, tmpboard, tmpsnake_size, food tmpsnake_size = snake_size tmpsnake = snake[:] # 如果直接tmpsnake=snake,則兩者指向同一處記憶體 tmpboard = board[:] # board中已經是各位置到達食物的路徑長度了,不用再計算 board_reset(tmpsnake, tmpsnake_size, tmpboard) 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 # 在蛇頭前加入一個新的位置 # 如果新加入的蛇頭的位置正好是食物的位置 # 則長度加1,重置board,食物那個位置變為蛇的一部分(SNAKE) if tmpsnake[HEAD] == food: tmpsnake_size += 1 board_reset(tmpsnake, tmpsnake_size, tmpboard) # 虛擬執行後,蛇在board的位置(label101010) tmpboard[food] = SNAKE food_eated = True else: # 如果蛇頭不是食物的位置,則新加入的位置為蛇頭,最後一個變為空格 tmpboard[tmpsnake[HEAD]] = SNAKE tmpboard[tmpsnake[tmpsnake_size]] = UNDEFINED # 如果蛇與食物間有路徑,則呼叫本函式 def find_safe_way(): global snake, board safe_move = ERR # 虛擬地執行一次,因為已經確保蛇與食物間有路徑,所以執行有效 # 執行後得到虛擬下蛇在board中的位置,即tmpboard,見label101010 virtual_shortest_move() # 該函式唯一呼叫處 if is_tail_inside(): # 如果虛擬執行後,蛇頭蛇尾間有通路,則選最短路執行(1步) return choose_shortest_safe_move(snake, board) safe_move = follow_tail() # 否則虛擬地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, '@') while key != 27: win.border(0) win.addstr(0, 2, 'S:' + str(score) + ' ') win.timeout(10) # 接收鍵盤輸入,同時也使顯示流暢 event = win.getch() key = key if event == -1 else event # 重置矩陣 board_reset(snake, snake_size, board) # 如果蛇可以吃到食物,board_refresh返回true # 並且board中除了蛇身(=SNAKE),其它的元素值表示從該點運動到食物的最短路徑長 if board_refresh(food, snake, board): best_move = find_safe_way() # find_safe_way的唯一呼叫處 else: best_move = follow_tail() if best_move == ERR: best_move = any_possible_move() # 上面一次思考,只得出一個方向,執行一步 if best_move != ERR: make_move(best_move) else: break curses.endwin() print("\nScore - " + str(score))