minesweeper.py

import itertools
import random


class Minesweeper():
    """
    Minesweeper game representation
    """

    def __init__(self, height=8, width=8, mines=8):

        # Set initial width, height, and number of mines
        self.height = height
        self.width = width
        self.mines = set()

        # Initialize an empty field with no mines
        self.board = []
        for i in range(self.height):
            row = []
            for j in range(self.width):
                row.append(False)
            self.board.append(row)

        # Add mines randomly
        while len(self.mines) != mines:
            i = random.randrange(height)
            j = random.randrange(width)
            if not self.board[i][j]:
                self.mines.add((i, j))
                self.board[i][j] = True

        # At first, player has found no mines
        self.mines_found = set()

    def print(self):
        """
        Prints a text-based representation
        of where mines are located.
        """
        for i in range(self.height):
            print("--" * self.width + "-")
            for j in range(self.width):
                if self.board[i][j]:
                    print("|X", end="")
                else:
                    print("| ", end="")
            print("|")
        print("--" * self.width + "-")

    def is_mine(self, cell):
        i, j = cell
        return self.board[i][j]

    def nearby_mines(self, cell):
        """
        Returns the number of mines that are
        within one row and column of a given cell,
        not including the cell itself.
        """

        # Keep count of nearby mines
        count = 0

        # Loop over all cells within one row and column
        for i in range(cell[0] - 1, cell[0] + 2):
            for j in range(cell[1] - 1, cell[1] + 2):

                # Ignore the cell itself
                if (i, j) == cell:
                    continue

                # Update count if cell in bounds and is mine
                if 0 <= i < self.height and 0 <= j < self.width:
                    if self.board[i][j]:
                        count += 1

        return count

    def won(self):
        """
        Checks if all mines have been flagged.
        """
        return self.mines_found == self.mines


class Sentence():
    """
    Logical statement about a Minesweeper game
    A sentence consists of a set of board cells,
    and a count of the number of those cells which are mines.
    """

    def __init__(self, cells, count):
        self.cells = set(cells)
        self.count = count

    def __eq__(self, other):
        return self.cells == other.cells and self.count == other.count

    def __str__(self):
        return f"{self.cells} = {self.count}"

    def known_mines(self):
        """
        Returns the set of all cells in self.cells known to be mines.
        """
        if len(self.cells) == self.count:
            return self.cells

    def known_safes(self):
        """
        Returns the set of all cells in self.cells known to be safe.
        """
        if len(self.cells) == 0:
            return self.cells

    def mark_mine(self, cell):
        """
        Updates internal knowledge representation given the fact that
        a cell is known to be a mine.
        """
        """
        if cell in self.cells:
            self.cells.remove(cell)
            self.count -= 1
        """
        new_Cells = set()
        for cells in self.cells:
            if cells != cell:
                new_Cells.add(cells)
            else:
                self.count -= 1
        self.cells = new_Cells

    def mark_safe(self, cell):
        """
        Updates internal knowledge representation given the fact that
        a cell is known to be safe.
        """

        # Previous code that resulted in modification of set during iteration in infer_new()
        """if cell in self.cells:
            self.cells.remove(cell)"""

        new_Cells = set()
        for cells in self.cells:
            if cells != cell:
                new_Cells.add(cells)
        self.cells = new_Cells

class MinesweeperAI():
    """
    Minesweeper game player
    """

    def __init__(self, height=8, width=8):

        # Set initial height and width
        self.height = height
        self.width = width

        # Keep track of which cells have been clicked on
        self.moves_made = set()

        # Keep track of cells known to be safe or mines
        self.mines = set()
        self.safes = set()

        # List of sentences about the game known to be true
        self.knowledge = []

    def mark_mine(self, cell):
        """
        Marks a cell as a mine, and updates all knowledge
        to mark that cell as a mine as well.
        """
        self.mines.add(cell)
        for sentence in self.knowledge:
            sentence.mark_mine(cell)

    def mark_safe(self, cell):
        """
        Marks a cell as safe, and updates all knowledge
        to mark that cell as safe as well.
        """
        self.safes.add(cell)
        for sentence in self.knowledge:
            sentence.mark_safe(cell)

    def add_knowledge(self, cell, count):
        """
        Called when the Minesweeper board tells us, for a given
        safe cell, how many neighboring cells have mines in them.

        This function should:
            1) mark the cell as a move that has been made
            2) mark the cell as safe
            3) add a new sentence to the AI's knowledge base
               based on the value of `cell` and `count`
            4) mark any additional cells as safe or as mines
               if it can be concluded based on the AI's knowledge base
            5) add any new sentences to the AI's knowledge base
               if they can be inferred from existing knowledge
        """
        # Step 1
        self.moves_made.add(cell)

        # Step 2
        self.mark_safe(cell)

        # Step 3

        # Add knowledge about neighbours if they contain at least one mine
        new_knowledge = Sentence(self.get_neighbours(cell), count)

        if new_knowledge.count > 0:
            possibleMines = set()
            for sentence in new_knowledge.cells:
                # If cell has already been determined to be a mine, decrease count
                if sentence in self.mines:
                    count -= 1

                # If cell is undetermined, add it to new set that will be converted to a sentence
                elif sentence not in self.mines and sentence not in self.safes:
                    possibleMines.add(sentence)

            newer_knowledge = Sentence(possibleMines, count)
            self.knowledge.append(newer_knowledge)


        # If neighbours are all safe, add them to safes
        if new_knowledge.count == 0:
            possibleSafes = set()
            for isSafe in new_knowledge.cells:
                if isSafe not in self.safes:
                    self.mark_safe(isSafe)

        # Adding new sentences to KB based on subsets
        for knowledge in self.knowledge:
            if knowledge.cells.issuperset(new_knowledge.cells):
                self.mark_and_include(knowledge, new_knowledge)

            elif new_knowledge.cells.issuperset(knowledge.cells):
                self.mark_and_include(new_knowledge, knowledge)

        # Inferring new knowledge
        self.infer_new()

    # Function that takes 2 sentences and checks for Mines/Safes to mark
    # Appends any new knowledge inferred
    def mark_and_include(self, cell1, cell2):

        CellDifference = cell1.cells - cell2.cells
        CountDifference = cell1.count - cell2.count

        # Check if remaining cells are safes
        if cell1.count == cell2.count:
            for isSafe in CellDifference:

                # Only add cells that are undetermined
                if isSafe not in self.safes:
                    self.mark_safe(isSafe)

        # Check if remaining cells are mines
        elif len(CellDifference) == CountDifference:
            for isMine in CellDifference:

                # Only add cells that are undetermined
                if isMine not in self.mines:
                    self.mark_mine(isMine)

        # Adds inferred knowledge to KB
        else:
            newer_knowledge = Sentence(CellDifference, CountDifference)
            if newer_knowledge not in self.knowledge:
                self.knowledge.append(newer_knowledge)

    # Infers new knowledge based on existing KB
    def infer_new(self):

        # Initialise an empty list to be used so as to not change size during iteration
        confirmed_knowledge = []
        for knowledge in self.knowledge:
            confirmed_knowledge.append(knowledge)

            if knowledge.known_mines():
                for foundMine in knowledge.known_mines():
                    self.mark_mine(foundMine)
                confirmed_knowledge.pop()

            elif knowledge.known_safes():
                for foundSafe in knowledge.known_safes():
                    self.mark_safe(foundSafe)
                confirmed_knowledge.pop()

        self.knowledge = confirmed_knowledge


    def make_safe_move(self):
        """
        Returns a safe cell to choose on the Minesweeper board.
        The move must be known to be safe, and not already a move
        that has been made.

        This function may use the knowledge in self.mines, self.safes
        and self.moves_made, but should not modify any of those values.
        """
        for move in self.safes:
            if move not in self.moves_made:
                return move

    def make_random_move(self):
        """
        Returns a move to make on the Minesweeper board.
        Should choose randomly among cells that:
            1) have not already been chosen, and
            2) are not known to be mines
        """
        # Initialise list of all available cells
        all_cells = []

        # Iterate through all cells, getting those that have not been selected and are not confirmed mines
        for i in range(self.height):
            for j in range(self.width):
                if (i, j) not in self.mines and (i, j) not in self.moves_made:
                    all_cells.append((i, j))

        if len(all_cells) == 0:
            return None

        return random.choice(all_cells)

    # Gets neighbours of a cell
    def get_neighbours(self, cell):
        i, j = cell
        # List of possible moves
        moves = [
            ('down', (i + 1, j)),
            ('downright', (i + 1, j + 1)),
            ('downleft', (i + 1, j - 1)),
            ('up', (i - 1, j)),
            ('upright', (i - 1, j + 1)),
            ('upleft', (i - 1, j - 1)),
            ('left', (i, j - 1)),
            ('right', (i, j + 1))
        ]

        # Initialise neighbours lsit
        neighbours = []
        for action, (r, c) in moves:

            # Check if action is within limit of height and width, and also if it has already been made
            if 0 <= r < self.height and 0 <= c < self.width and (r, c) not in self.moves_made:
                neighbours.append((r, c))

        return neighbours