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i am trying to learn python and have been trying to programm a simple tictactoe game.
Below is the code:
import random
class TicTacToe03:
def __init__(self):
# first, the board
self.board = self.board = [" ", " ", " ", " ", " ", " ", " ", " ", " "]
# then, the symbols the players will choose
self.playerSymbol = ""
self.aiSymbol = ""
# the game is always ongoing, unless somebody won
self.gameOngoing = True
# you also need to tell the ai how different conditions are evaluated
self.scoreBoard = {
self.playerSymbol: -10, # if the player wins, it is seen as smth bad from the ai
self.aiSymbol: 10,
"tie": 0
}
# every tictactoe game starts by drawing the board
def drawBoard(self):
print("""
{} | {} | {}
-----------
{} | {} | {}
-----------
{} | {} | {}
""".format(*self.board))
# then, eveybody chooses what the like
def chooseYourPlayer(self):
self.playerSymbol = input("choose your player X/O ").upper()
if self.playerSymbol == "X":
self.aiSymbol = "O"
else:
self.aiSymbol = "X"
# everybody has to behave and leave their turn when it's over
def nextPlayer(self, player):
if player == self.playerSymbol:
return self.aiSymbol
return self.playerSymbol
# ppl also have to be able to make moves
def move(self, player, index):
self.board[index] = player
# and find what moves they CAN make, so they don't override each-other
def availableMoves(self):
availableMoves = []
for fieldIndex in range(len(self.board)):
if self.board[fieldIndex] == " ":
availableMoves.append(fieldIndex) # yes, i append indexes, not empty fields
return availableMoves
def getMoves(self, player):
playerMoves = []
for fieldIndex in range(len(self.board)):
if self.board[fieldIndex] == player:
playerMoves.append(fieldIndex)
return playerMoves
# here is the algo to check who won, based on a set of winPos is subset of playerMoves
def won(self):
winningPositions = [{0, 1, 2}, {3, 4, 5}, {6, 7, 8},
{0, 4, 8}, {2, 4, 6}, {0, 3, 6},
{1, 4, 7}, {2, 5, 8}]
for player in ("X", "O"):
playerPositions = self.getMoves(player)
for position in winningPositions:
if position.issubset(playerPositions):
print(player + "wins")
self.gameOngoing = False
return player
if self.board.count(" ") == 0: # and this dude outside of the main loop
print("Guess it's a draw")
self.gameOngoing = False
return "tie"
def minimax(self, isMaximizing, player):
if not self.gameOngoing: # base in minimax: if this is an end-state, return it's evaluation
return self.scoreBoard[self.won()]
if isMaximizing:
bestScore = float("-Infinity") # the worst eval for max
for move in self.availableMoves():
self.move(player, move)
score = self.minimax(False, self.nextPlayer(player)) # you should pick the max of what your opponent chooses
self.move(" ", move)
bestScore = max(bestScore, score)
return bestScore
else:
bestScore = float("Infinity")
for move in self.availableMoves():
self.move(player, move)
score = self.minimax(True, self.nextPlayer(player))
self.move(" ", move)
bestScore = min(bestScore, score)
return bestScore
def findOptimalMove(self, player):
goldenMiddle = 0
choices = []
for move in self.availableMoves():
self.move(player, move)
score = self.minimax(True, player)
self.move(" ", move)
if score > goldenMiddle:
choices = [move] # this is a one-element list
break
elif score == goldenMiddle:
choices.append(move)
# here is the code block that mustn't be wrongly interpreted:
# the idea is: you choose a random element, from a ONE-ELEMENT list!!!
if len(choices) > 0:
return random.choice(choices)
else:
return random.choice(self.availableMoves())
def play(self):
self.chooseYourPlayer()
while self.gameOngoing:
personMove = int(input("Choose a position (1-9) "))
self.move(self.playerSymbol, personMove - 1)
self.drawBoard()
if not self.gameOngoing:
break
print("Computer choosing move...")
aiMove = self.findOptimalMove(self.aiSymbol)
self.move(self.aiSymbol, aiMove)
self.drawBoard()
print("Thanks for playing :)")
tictactoe = TicTacToe03()
tictactoe.play()
The game "works", as of it displays the fields of the user, however it won't show whether anybody won or not.
As you can see, i tried implementing the simple minimax algorithm, but that doesn't work properly either, because the ai just chooses the next available field to go to and not the one it logically should.
As for the errors i am getting: i only got one once, after the board was full and it was the following: IndexError: Cannot choose from an empty sequence (on line 133).
I have also posted another version of this, where the "winning" issue is not present ( TicTacToe and Minimax ), but since nobody was answering that question, I thought it would be helpful asking again (sorry if i did anything wrong)
As always, I remain open to suggestions and ways to improve my code :)
In my opinion, the only issue is that you forgot to call self.won() in the play() method:
def play(self):
self.chooseYourPlayer()
while self.gameOngoing:
personMove = int(input("Choose a position (1-9) "))
self.move(self.playerSymbol, personMove - 1)
self.drawBoard()
self.won() #<--- call self.won() here
if not self.gameOngoing:
break
print("Computer choosing move...")
aiMove = self.findOptimalMove(self.aiSymbol)
self.move(self.aiSymbol, aiMove)
self.drawBoard()
print("Thanks for playing :)")
I think you tried to do something similar in minimax() method. But I didn't understand what did you mean by:
if not self.gameOngoing:
return self.scoreBoard[self.won()]
I have an excercise to do and I'm stuck. It's the board game Alak, not much known, that I have to code in python. I can link the execrcise with the rules so you can help me better. The code has the main part and the library with all the procedures and function.
from Library_alak import *
n = 0
while n < 1:
n = int(input('Saisir nombre de case strictement positif : '))
loop = True
player = 1
player2 = 2
removed = [-1]
board = newboard(n)
display(board, n)
while loop:
i = select(board, n, player, removed)
print(i)
board = put(board, player, i)
display(board, n)
capture(board, n, player, player2)
loop = True if again(board, n, player, removed) is True else False
if player == 1 and loop:
player, player2 = 2, 1
elif player == 2 and loop:
player, player2 = 1, 2
win(board, n)
print(win(board, n))
And here is the library:
def newboard(n):
board = ([0] * n)
return board
def display(board, n):
for i in range(n):
if board[i] == 1:
print('X', end=' ')
elif board[i] == 2:
print('O', end=' ')
else:
print(' . ', end=' ')
def capture(board, n, player, player2):
for place in range(n):
if place == player:
place_beginning = place
while board[place] != player:
place_end = place
if board[place + x] == player:
return board
else:
return board
def again(board, n, player, removed):
for p in board(0):
if p == 0:
if p not in removed:
return True
else:
return False
def possible(n, removed, player, i, board):
for p in range(n + 1):
if p == 1:
if board[p-1] == 0:
if p not in removed:
return True
else:
return False
def win(board, n):
piecesp1 = 0
piecesp2 = 0
for i in board(0):
if i == 1:
piecesp1 += 1
else:
piecesp2 += 1
if piecesp1 > piecesp2:
print('Victory : Player 1')
elif piecesp2 > piecesp1:
print('Victory : Player 2')
else:
return 'Equality'
def select(board, n, player, removed):
loop = True
while loop:
print('player', player)
i = int(input('Enter number of boxes : '))
loop = False if possible(n, removed, player, i, board)is True else True
return i
def put(board, player, i):
i -= 1
if board[i] == 0:
if player == 1:
board[i] = 1
return board
else:
board[i] = 2
return board
else:
put(board, player, i)
So my problems here are that I have few errors, the first one is that when I enter the number '1' when asked to enter a number of boxes ( which is the place to play on ) nothing happens. Then when entering any other number, either the error is : if board[place + x] == player:
NameError: name 'x' is not defined
or there seems to be a problem with the : if board[place + x] == player:
NameError: name 'x' is not defined
I would appreciate a lot if anyone could help me. I'm conscious that it might not be as detailed as it should be and that you maybe don't get it all but you can contact me for more.
Rules of the Alak game:
Black and white take turns placing stones on the line. Unlike Go, this placement is compulsory if a move is available; if no move is possible, the game is over.
No stone may be placed in a location occupied by another stone, or in a location where a stone of your own colour has just been removed. The latter condition keeps the game from entering a neverending loop of stone placement and capture, known in Go as ko.
If placing a stone causes one or two groups of enemy stones to no longer have any adjacent empty spaces--liberties, as in Go--then those stones are removed. As the above rule states, the opponent may not play in those locations on their following turn.
If placing a stone causes one or two groups of your own colour to no longer have any liberties, the stones are not suicided, but instead are safe and not removed from play.
You shouldn't use "player2" as a variable, there's an easier way, just use "player" which take the value 1 or 2 according to the player. You know, something like that : player = 1 if x%2==0 else 2
and x is just a increasing int from 0 until the end of the game.
I'm trying to implement the minimax algorithm in my tic tac toe game. I watched several videos, analysed multiple programs with minimax algorithm and I think I do know how it works now. My program is working but it seems like the algorithm has no clue what he is doing. It outputs pads on the board but it doesn't block me or tries to win. Like it's random. It would be nice if someone could have a look at my minimax algorithm and tell what's wrong! It would also be nice to tell me whats wrong with my explanation and don't just downvote.
from copy import deepcopy
class Board:
def __init__(self, board=None):
self.winning_combos = (
[0, 1, 2], [3, 4, 5], [6, 7, 8],
[0, 3, 6], [1, 4, 7], [2, 5, 8],
[0, 4, 8], [2, 4, 6])
if board is not None:
self.board = board
else:
self.board = [None for i in range(9)]
def check_combos(self):
""" checks every combo if its used """
for symbol in ['X', 'O']:
for win_comb in self.winning_combos:
sum = 0
for field in win_comb:
if self.board[field] == symbol:
sum += 1
if sum == 3:
return symbol
return None
def complete(self):
""" check if the game is complete, caused by win or draw """
cc = self.check_combos()
if cc is not None:
return cc
if len(self.empty_pads()) <= 0:
return "DRAW"
return False
def show(self):
""" print board """
print(str(self.board[0:3]) + "\n" +
str(self.board[3:6]) + "\n" +
str(self.board[6:9]))
def empty_pads(self):
""" returns list with indexes of every unused/empty field/pad """
list = []
for pad in range(len(self.board)):
if self.board[pad] is None:
list.append(pad)
return list
def set(self, position, player):
""" sets the players symbol on the given position """
self.board[position] = player
def copy(self):
return deepcopy(self)
def get_enemy_player(player):
if player == 'X':
return 'O'
return 'X'
def get_player_value(player):
""" X = max, O = min """
if player == 'X':
return 1
else:
return -1
def get_player_by_value(value):
if value == -1:
return "O"
elif value == 1:
return "X"
else:
return "NONE"
def max_v(node):
if node.depth == 0 or node.board.complete():
return get_player_value(node.board.complete())
bestVal = -100
for child in node.children:
v = minimax(child)
if v >= bestVal:
bestVal = v
node.bestmove = child.move
return bestVal
def min_v(node):
if node.depth == 0 or node.board.complete():
return get_player_value(node.board.complete())
bestVal = 100
for child in node.children:
v = minimax(child)
if v <= bestVal:
bestVal = v
node.bestmove = child.move
return bestVal
def minimax(node):
if node.depth == 0 or node.board.complete():
return get_player_value(node.board.complete())
if get_player_value(node.player) == 1:
return max_v(node)
elif get_player_value(node.player) == -1:
return min_v(node)
class Node:
def __init__(self, depth, player, board, pad):
self.depth = depth
self.player = player
self.board = board
self.move = pad
self.board.set(pad, self.player)
self.bestmove = int
self.children = []
self.CreateChildren()
def CreateChildren(self):
if self.depth > 0 and not self.board.complete():
for index in self.board.empty_pads():
board = self.board.copy()
self.children.append(Node(self.depth - 1, get_enemy_player(self.player), board, index))
if __name__ == "__main__":
board = Board()
board.show()
while not board.complete():
player = 'X'
player_move = int(input('Move: ')) - 1
if player_move not in board.empty_pads():
continue
board.set(player_move, player)
board.show()
if board.complete():
break
player = get_enemy_player(player)
node = Node(9, player, board.copy(), player_move)
minmax = minimax(node)
print(node.bestmove+1)
for child in node.children:
print("move: " + str(child.move + 1) + " --> " + get_player_by_value(minmax) + " win")
board.set(node.bestmove, player)
board.show()
print(board.complete())
PS: I do know why the "moves: " ouput is always the same, but that's not the point.
I see multiple issues in your program.
As for your actual question: Your program acts as if the computer does not distinguish between a loss for it and a draw. Nowhere in your code can I find you assigning a value of 0 for a draw, while it appears you assign 1 for a win and -1 for a loss. Your code should prefer a draw to a loss but it sees no difference. That is why it looks "Like it's random". My analysis here may be off, but the following issues explain why it is difficult for me to tell.
Your style should be improved, to improve readability and ease of maintenance and to avoid bugs. Your code is much too difficult for me to understand, partly because...
You have far too few comments for anyone other than you to understand what the code is trying to do. In a few months you will not be able to remember, so write it down in the code.
You have too many blank lines, violating PEP8 and making harder to see much code on the screen.
You do not take your output seriously enough, as shown when you say "ou[t]put is always the same, but that's not the point." It is hard for anyone, including you, to tell what is happening in your code without good output. Work on that, and add some temporary print or logging statements that tell you more about what is happening inside.
Some of your routines return values of varying types. The complete() function sometimes returns the string "DRAW", sometimes the Boolean False, and sometimes a value from self.check_combos(), whatever type that is. Your routines max_v() and min_v() sometimes return a string value from get_player_value() and sometimes an integer from variable bestVal.
Python beginner here--working on a Battleship project for a class. My program will loop through the first player to place their ships. The grid does successfully print the visual ships on the board, but once i get to player two, the ships are overlapping with player one. (also note there is some validation work that still needs to be done).
I think the issue is that maybe I'm storing both coordinates for each player in the same list. So my question is how do I store the values for each player so that I can get the board to print ships only applicable to each player?
Here are my classes:
BOARD_SIZE = 10
class Ship:
def __init__(self, ship_name, size, coords, player, direction):
self.ship_name = ship_name
self.size = size
self.player = player
self.coords = coords
self.direction = direction
class Board:
def __init__(self):
self.board = []
self.guesses = []
board = [['O']*BOARD_SIZE for _ in range(BOARD_SIZE)]
def add_ship(self, name, size, player, coords, direction):
for coord in coords:
# convert string like "a1" to x,y coordinates
y = ord(coord[0])-ord('a')
x = int(coord[1:])-1
# update the board at this position
self.board = board[x][y]
print(" " + " ".join([chr(c) for c in range(ord('A'), ord('A') + BOARD_SIZE)]))
row_num = 1
for row in board:
print(str(row_num).rjust(2) + " " + (" ".join(row)))
row_num += 1
self.board.append(Ship(coords,player,name,size,direction))
def print_board_heading(self):
print(" " + " ".join([chr(c) for c in range(ord('A'), ord('A') + BOARD_SIZE)]))
def print_board(self):
board = [['O']*BOARD_SIZE for _ in range(BOARD_SIZE)]
print_board_heading()
row_num = 1
for row in board:
print(str(row_num).rjust(2) + " " + (" ".join(row)))
row_num += 1
def print_updated_board(coords, direction, board, player):
for coord in coords:
# convert string like "a1" to x,y coordinates
y = ord(coord[0])-ord('a')
x = int(coord[1:])-1
# update the board at this position
board[x][y] = '|' if direction == 'v' else '-'
print(" " + " ".join([chr(c) for c in range(ord('A'), ord('A') + BOARD_SIZE)]))
row_num = 1
for row in board:
print(str(row_num).rjust(2) + " " + (" ".join(row)))
row_num += 1
class Player():
def __init__(self,name):
self.name = name
self.board = Board()
self.ships = []
self.guesses = []
And the battleship game file:
from ship import Ship, Player, Board
SHIP_INFO = [
("Aircraft Carrier", 5),
("Battleship", 4),
("Submarine", 3),
("Cruiser", 3),
("Patrol Boat", 2)
]
BOARD_SIZE = 10
VERTICAL_SHIP = '|'
HORIZONTAL_SHIP = '-'
EMPTY = 'O'
MISS = '.'
HIT = '*'
SUNK = '#'
board = [['O']*BOARD_SIZE for _ in range(BOARD_SIZE)]
def print_board_heading():
print(" " + " ".join([chr(c) for c in range(ord('A'), ord('A') + BOARD_SIZE)]))
def print_board():
board = [['O']*BOARD_SIZE for _ in range(BOARD_SIZE)]
print_board_heading()
row_num = 1
for row in board:
print(str(row_num).rjust(2) + " " + (" ".join(row)))
row_num += 1
def print_updated_board(coords, direction,board):
# create an empty board
# board = [['O']*BOARD_SIZE for _ in range(BOARD_SIZE)]
# at each coordinate, draw a ship
for coord in coords:
# convert string like "a1" to x,y coordinates
y = ord(coord[0])-ord('a')
x = int(coord[1:])-1
# update the board at this position
board[x][y] = '|' if direction == 'v' else '-'
print_board_heading()
row_num = 1
for row in board:
print(str(row_num).rjust(2) + " " + (" ".join(row)))
row_num += 1
def clear_screen():
print("\033c", end="")
def get_coordinates(ship):
while True:
print("\n")
coordinate = input("Where do you want the " + ship + "(example: A1)?: ")
coords_strip = coordinate.strip()
coords_lower = coords_strip.lower()
x = coords_lower[0]
y = coords_lower[1:]
if (len(x)+len(y)) in range(2,4):
if x not in 'abcdefghij' or y not in '1,2,3,4,5,6,7,8,9,10':
print("Oops! That was not a valid entry. Try again...")
continue
else:
return x, y
else:
if len(coords_lower) < 2 or len(coords_lower) > 3:
print("Oops! That's too not the right amount of characters. Please try again...")
continue
def get_direction():
while True:
dir = input("[H]orizontal or [V]ertical?: ")
dir_strip = dir.strip()
direction = dir_strip.lower()
if direction not in 'hv':
print("Oops! That was not a valid entry. Try again...")
continue
else:
return direction
def create_ship_coordinates(x, y, size, direction):
ship_col = ord(x)
ship_row = int(y)
if direction == 'v':
# ship runs vertically DOWN from coordinate
coords = [chr(ship_col) + str(r) for r in range(ship_row, ship_row + size)]
return coords
else:
# ship runs horizontally RIGHT from coordinate
coords = [chr(col) + str(ship_row) for col in range(ship_col, ship_col + size)]
return coords
def place_user_ships(player):
ships = []
print_board()
print("\n")
print("Let's go " + player + " !")
for ship, size in SHIP_INFO:
while True:
# ask for starting coordinate
x, y = get_coordinates(ship)
# ask for vertical or horizontal direction
direction = get_direction()
# create the coordinates for the ship placement
coords = create_ship_coordinates(x, y, size, direction)
# validate the
# new_ship = Board().add_ship(ship, size, coords, direction, player)
# update = Board.print_updated_board(coords,direction,board,player)
break
# create ship from data
# add the ship from above to a player list
# player = Player(board)
# place the ship on the game board
# print out the board to reflect the shp placement
clear_screen()
print("\n")
input("All ships placed for {}. Please hit ENTER to continue....".format(player))
player1 = input("What's Player 1's Name? ")
player2 = input("What's Player 2's Name? ")
# define player one's fleet
place_user_ships(player1)
place_user_ships(player2)
IIRC, in battleship there are really four boards. One is managed by each player with their shots at the enemy, and the other is the player's own ships and incoming shots from the enemy.
The "shot" process is one of notifying the enemy where the shot was taken, the enemy responding with "hit" or "miss", and recording the result on the local player's outgoing-shots board.
The "notification" process is one of receiving a location where an enemy shot was made, looking up the result on the local-ships board, returning "hit" or "miss", and updating the local ships board to indicate the enemy shot.
So you have a Player, with a pair of Boards. You might also have a Game class to marry the two players.
Inputting the ships is going to depend a lot on your actual user interface. Are you doing graphics with a mouse? Are you doing text with a mouse? Text with arrow keys via curses or some such? Simple coordinate inputs?
If you're doing coordinates, you probably want something simple, like x,y,{up,down,left,right} to eliminate having to position every block of the ship.
Again, there is a Board method here - placing a ship. The board can enforce whatever rules you have about placement (ex: can two ships be directly adjacent? Or must there be a one-space gap between?) and reject the inappropriate attempts.
If you put all the wisdom in your Board class, then the Player classes can be simple, with just links to the boards. And the game can manage the players in turn:
def play(self):
p1 = self.player[0]
p2 = self.player[1]
try:
while True:
self.attack(p1, p2)
self.attack(p2, p1)
except Victory v:
print("The winner is", v.player.name)
I notice you doing things like player1 = input("What is player 1's name?"). This is something that should be pushed into the player classes.
Try to design from the top down: game, player, board. And try following the rule, "Tell, don't ask." That is, if something needs to be done, you tell a class to do it, instead of asking the class for data and doing it yourself.
Instead of this:
move = player1.get_move()
if valid_move(move):
...
Do this:
player1.make_move()
And push the logic downwards. Eventually, you get to the place where the knowledge "should be". The player "should" make moves. The board "should" know what is a valid move or not. And every method "should" be given enough data to do its job. ;-)
So, I have an assignment which asks me to solve a maze using recursion. I will post the assignment guidelines so you can see what I am talking about. The professor didn't explain recursion that much, he gave us examples of recursion, which I will post, but I was hoping someone might be able to give me a more in depth explanation of the recursion, and how I would apply this to solving a maze. I'm not asking for anyone to write the code, I'm just hoping some explanations would put me on the right path. Thank you to anyone who answers.
Here are the examples I have:
def foo():
print("Before")
bar()
print("After")
def bar():
print("During")
def factorial(n):
"""n!"""
product = 1
for i in range(n,0,-1):
product *= i
return product
def recFac(n):
"""n! = n * (n-1)!"""
if(n == 1):
return 1
return n * recFac(n-1)
def hello():
"""Stack overflow!"""
hello()
def fib(n):
"""f(n) = f(n-1) + f(n-2)
f(0) = 0
f(1) = 1"""
if n == 0 or n == 1: #base case
return n
return fib(n-1) + fib(n-2) #recursive case
def mult(a,b):
"""a*b = a + a + a + a ..."""
#base case
if (b == 1):
return a
#recursive case
prod = mult(a,b-1)
prod *= a
return prod
def exp(a,b):
"""a ** b = a* a * a * a * a *.... 'b times'"""
#base case
if (b==0):
return 1
if (b == 1):
return a
#recursive case
return exp(a,b-1)*a
def pallindrome(word):
"""Returns True if word is a pallindrome, False otherwise"""
#base case
if word == "" or len(word)==1:
return True
#recursive case
if word[0] == word[len(word)-1]:
word = word[1:len(word)-1]
return pallindrome(word)
else:
return False
Here are the guidelines:
You are going to create a maze crawler capable of solving any maze you give it with the power of recursion!
Question 1 - Loading the maze
Before you can solve a maze you will have to load it. For this assignment you will use a simple text format for the maze. You may use this sample maze or create your own.
Your objective for this question is to load any given maze file, and read it into a 2-dimensional list.
E.g.: loadMaze("somemaze.maze") should load the somemaze.maze file and create a list like the following...
[['#','#','#','#','#','#','#','#','#'],
['#','S','#',' ',' ',' ','#','E','#'],
['#',' ','#',' ','#',' ',' ',' ','#'],
['#',' ',' ',' ','#',' ','#',' ','#'],
['#', #','#','#','#','#','#','#','#']]
Note that the lists have been stripped of all '\r' and '\n' characters. In order to make the next question simpler you may make this list a global variable.
Next write a function that prints out the maze in a much nicer format:
E.g.,
####################################
#S# ## ######## # # # # #
# # # # # # #
# # ##### ## ###### # ####### # #
### # ## ## # # # #### #
# # # ####### # ### #E#
####################################
Test your code with different mazes before proceeding.
Question 2 - Preparing to solve the maze
Before you can solve the maze you need to find the starting point! Add a function to your code called findStart() that will search the maze (character-by-character) and return the x and y coordinate of the 'S' character. You may assume that at most one such character exists in the maze. If no 'S' is found in the maze return -1 as both the x and y coordinates.
Test your code with the 'S' in multiple locations (including no location) before proceeding.
Question 3 - Solving the maze!
Finally, you are ready to solve the maze recursively! Your solution should only require a single method: solve(y,x)
A single instance of the solve method should solve a single location in your maze. The parameters y and x are the current coordinates to be solved. There are a few things your solve method should accomplish. It should check if it is currently solving the location of the 'E'. In that case your solve method has completed successfully. Otherwise it should try to recursively solve the space to the right. Note, your method should only try to solve spaces, not walls ('#'). If that recursion doesn't lead to the end, then try down, then left, and up. If all that fails, your code should backtrack a step, and try another direction.
Lastly, while solving the maze, your code should leave indicators of its progress. If it is searching to the right, the current location should have a '>' in place of the empty space. If searching down put a 'v'. If searching left '<', and if searching up '^'. If your code has to backtrack remove the direction arrow, and set the location back to a ' '.
Once your maze is solved print out the maze again. You should a see step-by-step guide to walking the maze.
E.g.,
main("somemaze.maze")
#########
#S# #E#
# # # #
# # # #
#########
S is at (1,1)
#########
#S#>>v#E#
#v#^#>>^#
#>>^# # #
#########
Test your code with different different start and end locations, and optionally over a variety of mazes.
Here is the code I have so far:
But the code is not actually printing the track in the maze, and I'm not sure why.
def loadMaze():
readIt = open('Maze.txt', 'r')
readLines = readIt.readlines()
global mazeList
mazeList = [list(i.strip()) for i in readLines]
def showMaze():
for i in mazeList:
mazeprint = ''
for j in i:
mazeprint = mazeprint + j
print(mazeprint)
print('\n')
def solve(x,y, mazeList):
mazeList[x][y] = "o"
#Base case
if y > len(mazeList) or x > len(mazeList[y]):
return False
if mazeList[y][x] == "E":
return True
if mazeList[y][x] != " ":
return False
#marking
if solve(x+1,y) == True: #right
mazeList[x][y]= '>'
elif solve(x,y+1) == True: #down
mazeList[x][y]= 'v'
elif solve(x-1,y) == True: #left
mazeList[x][y]= '<'
elif solve(x,y-1) == True: #up
mazeList[x][y]= '^'
else:
mazeList[x][y]= ' '
return (mazeList[x][y]!= ' ')
(Dating myself, I actually did this problem in COBOL, in high-school.)
You can think of solving the maze as taking steps.
When you take a step, the same rules apply every time. Because the same rules apply every time, you can use the exact same set of instructions for each step. When you take a step, you just call the same routine again, changing the parameters to indicate the new step. That's recursion. You break the problem down by taking it one step at a time.
Note: Some recursion solutions break the problem in half, solving each half independent of the other, that works when the two solutions are actually independent. It doesn't work here because each step (solution) depends on the previous steps.
If you hit a dead end, you back out of the dead end, until you find a step where there are still viable squares to check.
Helpful Hint: You don't mark the correct path on the way to the exit, because you don't know that the step you're taking right now is part of the path to the exit. You mark the path on the way back, when you know that each step is indeed part of the path. You can do this because each step remembers which square it was in before it took the next step.
Instead, you put a mark in each square you've tried that only says: I've been here, no need to check this one again. Clean those up before you print the solution.
Here is my solution of CodeEval's The Labirynth challenge:
import sys
sys.setrecursionlimit(5000)
class Maze(object):
FLOOR = ' '
WALLS = '*'
PATH = '+'
def __init__(self):
self.cols = 0
self.rows = 0
self.maze = []
def walk_forward(self, current_k, r, c):
self.maze[r][c] = current_k
next_k = current_k + 1
# up
if r > 1:
up = self.maze[r - 1][c]
if up != self.WALLS:
if up == self.FLOOR or int(up) > current_k:
self.walk_forward(next_k, r - 1, c)
# down
if r < self.rows - 1:
down = self.maze[r + 1][c]
if down != self.WALLS:
if down == self.FLOOR or int(down) > current_k:
self.walk_forward(next_k, r + 1, c)
# left
if c > 1:
left = self.maze[r][c - 1]
if left != self.WALLS:
if left == self.FLOOR or int(left) > current_k:
self.walk_forward(next_k, r, c - 1)
# right
if c < self.cols - 1:
right = self.maze[r][c + 1]
if right != self.WALLS:
if right == self.FLOOR or int(right) > current_k:
self.walk_forward(next_k, r, c + 1)
def walk_backward(self, r, c):
current_k = self.maze[r][c]
if not isinstance(current_k, int):
return False
self.maze[r][c] = self.PATH
up = self.maze[r - 1][c] if r > 0 else None
down = self.maze[r + 1][c] if r < self.rows - 1 else None
left = self.maze[r][c - 1] if c > 1 else None
right = self.maze[r][c + 1] if c < self.cols else None
passed = False
if up and isinstance(up, int) and up == current_k - 1:
self.walk_backward(r - 1, c)
passed = True
if down and isinstance(down, int) and down == current_k - 1:
self.walk_backward(r + 1, c)
passed = True
if left and isinstance(left, int) and left == current_k - 1:
self.walk_backward(r, c - 1)
passed = True
if right and isinstance(right, int) and right == current_k - 1:
self.walk_backward(r, c + 1)
def cleanup(self, cleanup_path=False):
for r in range(0, self.rows):
for c in range(0, self.cols):
if isinstance(self.maze[r][c], int):
self.maze[r][c] = self.FLOOR
if cleanup_path and self.maze[r][c] == self.PATH:
self.maze[r][c] = self.FLOOR
def solve(self, start='up', show_path=True):
# finding start and finish points
upper = lower = None
for c in range(0, self.cols):
if self.maze[0][c] == self.FLOOR:
upper = (0, c)
break
for c in range(0, self.cols):
if self.maze[self.rows - 1][c] == self.FLOOR:
lower = (self.rows - 1, c)
break
if start == 'up':
start = upper
finish = lower
else:
start = lower
finish = upper
self.cleanup(cleanup_path=True)
self.walk_forward(1, start[0], start[1])
length = self.maze[finish[0]][finish[1]]
if not isinstance(length, int):
length = 0
if show_path:
self.walk_backward(finish[0], finish[1])
self.cleanup(cleanup_path=False)
else:
self.cleanup(cleanup_path=True)
return length
def save_to_file(self, filename):
with open(filename, 'w') as f:
f.writelines(str(self))
def load_from_file(self, filename):
self.maze = []
with open(filename, 'r') as f:
lines = f.readlines()
for line in lines:
row = []
for c in line.strip():
row.append(c)
self.maze.append(row)
self.rows = len(self.maze)
self.cols = len(self.maze[0]) if self.rows > 0 else 0
def get_maze(self):
return copy.copy(self.maze)
def __str__(self):
as_string = u''
for row in self.maze:
as_string += u''.join([str(s)[-1] for s in row]) + "\n"
return as_string
maze = Maze()
maze.load_from_file(sys.argv[1])
maze.solve(show_path=True)
print str(maze)
import os
class Maze_Crawler:
def __init__(self):
self.maze = []
def load_maze(self, path):
rows = []
with open(path, 'r') as f:
rows = f.readlines()
for i in range(len(rows)):
self.maze.append([])
for j in range(len(rows[i])-1):
self.maze[i].append(rows[i][j])
return self.maze
def get_start_coor(self):
for i in range(len(self.maze)):
for j in range(len(self.maze[i])):
if self.maze[i][j] == 'S':
return i, j
return -1, -1
def solve_maze(self, coor):
x, y = coor
if self.maze[x][y] == '#' or self.maze[x][y] == 'X':
return False
if self.maze[x][y] == 'E':
return True
if self.maze[x][y] != 'S':
self.maze[x][y] = 'X'
if self.solve_maze((x+1, y)):
if self.maze[x][y] != 'S':
self.maze[x][y] = 'v'
elif self.solve_maze((x-1, y)):
if self.maze[x][y] != 'S':
self.maze[x][y] = '^'
elif self.solve_maze((x, y+1)):
if self.maze[x][y] != 'S':
self.maze[x][y] = '>'
elif self.solve_maze((x, y-1)):
if self.maze[x][y] != 'S':
self.maze[x][y] = '<'
else:
return False
return True
def show_solution(self):
for i in range(len(self.maze)):
r = ''
for j in range(len(self.maze[i])):
if self.maze[i][j] == 'X':
r += ' '
else:
r += self.maze[i][j]
print(r)
Maze solving with python shows my answer. However, if you want to do the code yourself the steps are.
1. Start at the entrance.
2. Call the function solve(x,y) with the entrance co-ordinates
3. in solve, return false if the input point has already been handled or is a wall.
4. Mark the current point as handled (tag = 'o')
5. go to the right and call solve on that point. If it returns true, set tag to '>'
6 elif do the same for left and '<'
7 elif do the same for up and '^'
8 elif do the same for down and 'v'
9 else this is a false path, set tag = ' '
10 set the current maze point to tag
11 return (tag != ' ')
Alternatively leave step 9 out and make step 11
return(tag != 'o')
Then search through the maze and replace every 'o' with ' '
You can display the maze both ways so that it will show how you tried to solve it as well as the final answer. This has been used as a Solaris screensaver with the potential paths showing in one color and the actual path in a different color so that you can see it trying and then succeeding.
Recursion is actually a simple idea: to solve a problem, you shrink the problem by one step, then solve the reduced problem. This continues until you reach a "base problem" that you know how to solve completely. You return the base solution, then add to the solution returned at each step until you have the full solution.
So to solve n!, we remember n and solve for (n-1)!. The base case is 1!, for which we return 1; then at each return step we multiply by the remembered number (2 * 1! is 2, 3 * 2! is 6, 4 * 3! is 24, 5 * 4! is 120) until we multiply by n and have the full solution. This is actually a pretty pale and anemic sort of recursion; there is only one possible decision at each step. Known as "tail recursion", this is very easy to turn inside-out and convert to an iterative solution (start at 1 and multiply by each number up to n).
A more interesting sort of recursion is where you split the problem in half, solve each half, then combine the two half-solutions; for example quicksort sorts a list by picking one item, dividing the list into "everything smaller than item" and "everything bigger than item", quicksorting each half, then returning quicksorted(smaller) + item + quicksorted(larger). The base case is "when my list is only one item, it is sorted".
For the maze, we are going to split the problem four ways - all solutions possible if I go right, left, up, and down from my current location - with the special feature that only one of the recursive searches will actually find a solution. The base case is "I am standing on E", and a failure is "I am in a wall" or "I am on a space I have already visited".
Edit: for interest's sake, here is an OO solution (compatible with both Python 2.x and 3.x):
from collections import namedtuple
Dir = namedtuple("Dir", ["char", "dy", "dx"])
class Maze:
START = "S"
END = "E"
WALL = "#"
PATH = " "
OPEN = {PATH, END} # map locations you can move to (not WALL or already explored)
RIGHT = Dir(">", 0, 1)
DOWN = Dir("v", 1, 0)
LEFT = Dir("<", 0, -1)
UP = Dir("^", -1, 0)
DIRS = [RIGHT, DOWN, LEFT, UP]
#classmethod
def load_maze(cls, fname):
with open(fname) as inf:
lines = (line.rstrip("\r\n") for line in inf)
maze = [list(line) for line in lines]
return cls(maze)
def __init__(self, maze):
self.maze = maze
def __str__(self):
return "\n".join(''.join(line) for line in self.maze)
def find_start(self):
for y,line in enumerate(self.maze):
try:
x = line.index("S")
return y, x
except ValueError:
pass
# not found!
raise ValueError("Start location not found")
def solve(self, y, x):
if self.maze[y][x] == Maze.END:
# base case - endpoint has been found
return True
else:
# search recursively in each direction from here
for dir in Maze.DIRS:
ny, nx = y + dir.dy, x + dir.dx
if self.maze[ny][nx] in Maze.OPEN: # can I go this way?
if self.maze[y][x] != Maze.START: # don't overwrite Maze.START
self.maze[y][x] = dir.char # mark direction chosen
if self.solve(ny, nx): # recurse...
return True # solution found!
# no solution found from this location
if self.maze[y][x] != Maze.START: # don't overwrite Maze.START
self.maze[y][x] = Maze.PATH # clear failed search from map
return False
def main():
maze = Maze.load_maze("somemaze.txt")
print("Maze loaded:")
print(maze)
try:
sy, sx = maze.find_start()
print("solving...")
if maze.solve(sy, sx):
print(maze)
else:
print(" no solution found")
except ValueError:
print("No start point found.")
if __name__=="__main__":
main()
and when run produces:
Maze loaded:
####################################
#S# ## ######## # # # # #
# # # # # # #
# # ##### ## ###### # ####### # #
### # ## ## # # # #### #
# # # ####### # ### #E#
####################################
solving...
####################################
#S# ## ######## # #>>>>>v# >>v# #
#v#>>v# >>>v #^# >>>>^#>>v#
#>>^#v#####^##v######^# ####### #v#
### #v##>>>^##>>>>>v#^# # ####v#
# #>>>^# #######>>^# ### #E#
####################################
Note that the assignment as given has a few unPythonic elements:
it asks for camelCase function names rather than underscore_separated
it suggests using a global variable rather than passing data explicitly
it asks for find_start to return flag values on failure rather than raising an exception