chat

🔍

question:# Tic-Tac-Toe Validator Context You are tasked with creating a validator for a game of Tic-Tac-Toe. The game is played on a 3x3 grid, and the players take turns marking a cell with either 'X' or 'O'. The objective is for a player to place three of their marks in a horizontal, vertical, or diagonal row to win the game. If all cells are filled and no player has achieved this, the game is a draw. Task Implement a class `TicTacToe` in Python that supports the following operations: 1. Initialization of an empty Tic-Tac-Toe board. 2. Adding a move to the board. 3. Checking the current state of the game (win, draw, or ongoing). 4. Retrieving the current state of the board as a string. Requirements 1. **Initialization**: - The constructor should initialize an empty 3x3 board. ```python def __init__(self) -> None: ``` 2. **Make a Move**: - The method should take the row and column numbers (0-based) and the player's mark ('X' or 'O'). - Raise a `ValueError` if the cell is already occupied or if the row/column numbers are out of bounds. ```python def make_move(self, row: int, col: int, player: str) -> None: ``` 3. **Check Game State**: - The method should return 'X' if player 'X' has won, 'O' if player 'O' has won, 'Draw' if all cells are filled and there's no winner, or 'Ongoing' if the game is still in progress. ```python def get_game_state(self) -> str: ``` 4. **String Representation**: - The method should return a string representation of the current board state. ```python def __str__(self) -> str: ``` Example: ```python game = TicTacToe() print(game) # Should display an empty Tic-Tac-Toe board game.make_move(0, 0, 'X') print(game) # Should display the board with 'X' in the top-left corner game.make_move(1, 1, 'O') print(game) # Should display the board with 'O' in the center state = game.get_game_state() print(state) # Should return 'Ongoing' game.make_move(0, 1, 'X') game.make_move(0, 2, 'X') state = game.get_game_state() print(state) # Should return 'X' after the winning move ``` Constraints: - Ensure that only valid moves are accepted. - The board state should be correctly updated after each move. - The game should correctly identify all possible winning states (horizontal, vertical, diagonal). Input and Output Formats: - **Initialization**: `TicTacToe()` initializes an empty board. - **Make a Move**: `game.make_move(0, 0, 'X')` updates the board with 'X' at position (0, 0). - **Check Game State**: `game.get_game_state()` returns 'X', 'O', 'Draw', or 'Ongoing'. - **String Representation**: `print(game)` returns a string showing the current board. By adhering to these guidelines, create and verify the `TicTacToe` class to ensure its functionality. Using this set, expand on supplemental concepts such as game-state validation logic, user error handling, and clear encapsulation of game mechanics.

answer:class TicTacToe: def __init__(self): self.board = [[' ' for _ in range(3)] for _ in range(3)] self.moves_count = 0 def make_move(self, row: int, col: int, player: str) -> None: if player not in ['X', 'O']: raise ValueError("Player must be 'X' or 'O'") if not (0 <= row < 3 and 0 <= col < 3): raise ValueError("Row and column must be between 0 and 2") if self.board[row][col] != ' ': raise ValueError("Cell already occupied") self.board[row][col] = player self.moves_count += 1 def get_game_state(self) -> str: # Check rows for row in self.board: if row[0] == row[1] == row[2] != ' ': return row[0] # Check columns for col in range(3): if self.board[0][col] == self.board[1][col] == self.board[2][col] != ' ': return self.board[0][col] # Check diagonals if self.board[0][0] == self.board[1][1] == self.board[2][2] != ' ': return self.board[0][0] if self.board[0][2] == self.board[1][1] == self.board[2][0] != ' ': return self.board[0][2] # Check draw if self.moves_count == 9: return 'Draw' # Game ongoing return 'Ongoing' def __str__(self) -> str: return 'n'.join([' '.join(row) for row in self.board])

question:# Basic Statistical Functions Package You are tasked with implementing a small package that provides basic statistical functions. Your package should include functions for computing the mean, median, and standard deviation of a list of numbers. Ensure your implementations are efficient and handle edge cases appropriately. Objective Create a Python package with three functions: `mean`, `median`, and `std_dev`. These functions should compute the respective statistical measures for a given list of numerical values. # Tasks 1. **mean(values)**: - Computes the average of the provided list of numbers. - Handles empty lists by returning `None`. 2. **median(values)**: - Returns the median value of the provided list of numbers. - Ensures the function handles both even and odd list lengths. - Handles empty lists by returning `None`. 3. **std_dev(values)**: - Computes the standard deviation of the list. - Uses the sample standard deviation formula. - Handles lists with fewer than two elements by returning `None`. # Input/Output - **mean function**: - **Input**: - `values`: A list of numerical values. - **Output**: A single floating-point number representing the mean or `None` for an empty list. - **median function**: - **Input**: - `values`: A list of numerical values. - **Output**: A single floating-point number representing the median or `None` for an empty list. - **std_dev function**: - **Input**: - `values`: A list of numerical values. - **Output**: A single floating-point number representing the standard deviation or `None` for lists of length less than two. # Constraints - The input list contains only numerical values (integers or floats). - The functions should handle edge cases such as empty lists or small list lengths gracefully. # Sample Usage ```python values = [2, 5, 1, 3, 4] print(mean(values)) # Expected output: 3.0 print(median(values)) # Expected output: 3.0 print(std_dev(values)) # Expected output: 1.58 (approximately) empty_list = [] print(mean(empty_list)) # Expected output: None print(median(empty_list)) # Expected output: None print(std_dev(empty_list)) # Expected output: None ``` # Considerations - Ensure that your functions are efficient and handle various edge cases. - Avoid using external libraries; rely on core Python functionality. - Ensure appropriate error handling and input validation. Write your implementation of the `mean`, `median`, and `std_dev` functions below.

answer:def mean(values): Computes the mean (average) of a list of numbers. :param values: List of numerical values :return: Mean of the values or None for an empty list if not values: return None return sum(values) / len(values) def median(values): Computes the median of a list of numbers. :param values: List of numerical values :return: Median of the values or None for an empty list if not values: return None sorted_values = sorted(values) length = len(sorted_values) midpoint = length // 2 if length % 2 == 0: return (sorted_values[midpoint - 1] + sorted_values[midpoint]) / 2.0 else: return sorted_values[midpoint] def std_dev(values): Computes the sample standard deviation of a list of numbers. :param values: List of numerical values :return: Standard deviation of the values or None for lists of length less than two if len(values) < 2: return None mean_val = mean(values) variance = sum((x - mean_val) ** 2 for x in values) / (len(values) - 1) return variance ** 0.5

question:# URL Shortener You are tasked with creating a URL shortener function. The function should generate a short unique URL for a given long URL and store the mapping of the short URL to the long URL. You should also provide a way to retrieve the original long URL given a short URL. For simplicity, assume you can use an in-memory dictionary to store the mappings. # Function Signatures ```python def shorten_url(long_url: str) -> str: ... def retrieve_long_url(short_url: str) -> str: ... ``` # Input Descriptions 1. `long_url` (str): The original URL that needs to be shortened. 2. `short_url` (str): The shortened URL that was previously generated. # Output Descriptions 1. `shorten_url(long_url: str) -> str`: Returns the shortened URL. 2. `retrieve_long_url(short_url: str) -> str`: Returns the original long URL that corresponds to the given short URL. # Constraints 1. If the provided long URL is already shortened, return the existing short URL. 2. If the provided short URL does not exist in the storage, the function should raise a `ValueError` with an appropriate message. 3. Assume the short URL will have a base domain of `http://short.url/` followed by a unique identifier. # Example ```python shortened = shorten_url("https://www.example.com") print(shortened) # Expected output: "http://short.url/abc123" original = retrieve_long_url("http://short.url/abc123") print(original) # Expected output: "https://www.example.com" # Querying an unknown short URL try: retrieve_long_url("http://short.url/unknown") except ValueError as e: print(e) # Expected output: "Short URL does not exist." ``` # Additional Information 1. Use a suitable algorithm to generate unique identifiers for the short URLs. 2. You may use the `hashlib` module to create hashes if desired. 3. Ensure that your implementation efficiently handles multiple long URLs and provides fast retrieval times. 4. Include necessary error handling for invalid URLs. If the input for long_url is not a valid URL format, the function should raise a `ValueError`. # Expected Implementation ```python import hashlib url_mapping = {} reverse_mapping = {} def shorten_url(long_url: str) -> str: # Validate the URL format (simplified check just for illustration) if not long_url.startswith(('http://', 'https://')): raise ValueError('Invalid URL format') if long_url in reverse_mapping: return reverse_mapping[long_url] # Generate a short identifier using hashing (e.g., MD5 or SHA256) hasher = hashlib.md5(long_url.encode()) short_id = hasher.hexdigest()[:6] # e.g., "abc123" short_url = f"http://short.url/{short_id}" url_mapping[short_url] = long_url reverse_mapping[long_url] = short_url return short_url def retrieve_long_url(short_url: str) -> str: if short_url not in url_mapping: raise ValueError("Short URL does not exist.") return url_mapping[short_url] ``` This question challenges the applicant to implement a URL shortener utility which involves string processing, dictionary management, and basic hashing techniques. It tests their ability to handle mappings and error conditions, ensuring the robustness of their solution.

answer:import hashlib url_mapping = {} reverse_mapping = {} def shorten_url(long_url: str) -> str: Generate a short unique URL for a given long URL and store the mapping of the short URL to the long URL. # Validate the URL format (simplified check) if not long_url.startswith(('http://', 'https://')): raise ValueError('Invalid URL format') # Return the existing short URL if the long URL was already shortened if long_url in reverse_mapping: return reverse_mapping[long_url] # Generate a short identifier using hashing (MD5) hasher = hashlib.md5(long_url.encode()) short_id = hasher.hexdigest()[:6] # e.g., "abc123" short_url = f"http://short.url/{short_id}" # Store the mappings url_mapping[short_url] = long_url reverse_mapping[long_url] = short_url return short_url def retrieve_long_url(short_url: str) -> str: Retrieve the original long URL given a short URL. if short_url not in url_mapping: raise ValueError("Short URL does not exist.") return url_mapping[short_url]

question:# Circular Buffer Implementation You are tasked with implementing a circular buffer (or ring buffer) data structure in Python. A circular buffer is a fixed-size data structure that works as a FIFO (first-in, first-out) queue but optimizes space by riding over the oldest elements when new elements are added to the buffer that is already full. # Input Your task is to write a class `CircularBuffer` with the following methods: 1. **__init__(self, size)**: Initializes the buffer with a given size. 2. **insert(self, value)**: Inserts an element into the buffer. If the buffer is full, it should overwrite the oldest element. 3. **get(self)**: Retrieves and removes the oldest element from the buffer. Returns `None` if the buffer is empty. 4. **__str__(self)**: Returns a string representation of the buffer contents in the insertion order, from oldest to newest. # Constraints * The size of the buffer is a positive integer (1 <= size <= 1000). * The values inserted into the buffer are integers. * Ensure efficient utilization of computational resources and minimize unnecessary operations. # Example ```python # Create a circular buffer of size 3 buffer = CircularBuffer(3) # Insert elements into the buffer buffer.insert(10) buffer.insert(20) buffer.insert(30) # The buffer is now [10, 20, 30] print(str(buffer)) # Output: "10, 20, 30" # Get the oldest element (10) print(buffer.get()) # Output: 10 # Insert a new element, overwriting the oldest element (20) buffer.insert(40) # The buffer is now [20, 30, 40] print(str(buffer)) # Output: "20, 30, 40" # Continue getting elements print(buffer.get()) # Output: 20 print(buffer.get()) # Output: 30 print(buffer.get()) # Output: 40 # The buffer is now empty print(buffer.get()) # Output: None ``` # Implementation Hints * Use a fixed-size list to represent the buffer and maintain pointers/indexes to track the start and end positions for insertion and retrieval. * Be sure to handle edge cases, such as inserting into a full buffer and retrieving from an empty buffer, efficiently. Write a `CircularBuffer` class with the specified methods ensuring the buffer operates as described.

answer:class CircularBuffer: def __init__(self, size): Initializes the buffer with a given size. self.size = size self.buffer = [None] * size self.start = 0 self.end = 0 self.count = 0 def insert(self, value): Inserts an element into the buffer. If the buffer is full, it overwrites the oldest element. if self.count == self.size: self.start = (self.start + 1) % self.size else: self.count += 1 self.buffer[self.end] = value self.end = (self.end + 1) % self.size def get(self): Retrieves and removes the oldest element from the buffer. Returns None if the buffer is empty. if self.count == 0: return None value = self.buffer[self.start] self.buffer[self.start] = None self.start = (self.start + 1) % self.size self.count -= 1 return value def __str__(self): Returns a string representation of the buffer contents in the insertion order, from oldest to newest. elements = [] index = self.start for _ in range(self.count): elements.append(self.buffer[index]) index = (index + 1) % self.size return ", ".join(str(e) for e in elements)