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question:# Checks if the input string is a palindrome Step 1: Define the Problem The problem requires a function that takes a string as input and returns True if the string is a palindrome, and False otherwise. A palindrome is a word, phrase, number, or other sequence of characters that reads the same forward and backward (ignoring spaces, punctuation, and capitalization). Step 2: Plan the Solution Strategy To solve this problem, we will create a function that first cleans the input string by removing spaces and punctuation, and converting it to lower case. Then, it will compare the cleaned string with its reverse. If they are the same, the function will return True; otherwise, it will return False. Step 3: Implement the Solution in Python We can implement this solution using Python. We will use the `re` module to remove spaces and punctuation, and slicing to reverse the string. ```python import re def is_palindrome(s): # Remove spaces and punctuation, and convert to lower case cleaned_s = re.sub(r'W+', '', s).lower() # Compare the cleaned string with its reverse return cleaned_s == cleaned_s[::-1] ``` Step 4: Test the Function We can test the function with some examples to ensure it works correctly. ```python print(is_palindrome("A man, a plan, a canal: Panama")) # True print(is_palindrome("Not a palindrome")) # False print(is_palindrome("Was it a car or a cat I saw?
answer:import re def is_palindrome(s): Returns True if the input string is a palindrome, otherwise False. A palindrome is a word, phrase, number, or other sequence of characters that reads the same forward and backward (ignoring spaces, punctuation, and capitalization). # Remove spaces and punctuation, and convert to lower case cleaned_s = re.sub(r'W+', '', s).lower() # Compare the cleaned string with its reverse return cleaned_s == cleaned_s[::-1]
question:This problem is taken from LeetCode, here is the link https://leetcode.com/problems/clone-graph/, it is in medium level clones the nodes of a given graph and then connects them to each other ```python # Definition for a Node. class Node: def __init__(self, val = 0, neighbors = None): self.val = val self.neighbors = neighbors if neighbors is not None else [] class Solution: def cloneGraph(self, node: 'Node') -> 'Node': if node is None: return node visited = {} def dfs(node): if node.val in visited: return visited[node.val] copy = Node(node.val, []) visited[node.val] = copy if node.neighbors: copy.neighbors = [dfs(n) for n in node.neighbors] return copy return dfs(node) ``` In the above code, `visited` is a dictionary which stores the old nodes as keys and the cloned nodes as values. However, this code is using the node's value as the key in the `visited` dictionary which could be problematic if there are two or more nodes with the same value in the graph. How can we avoid this issue?
answer:class Node: def __init__(self, val = 0, neighbors = None): self.val = val self.neighbors = neighbors if neighbors is not None else [] class Solution: def cloneGraph(self, node: 'Node') -> 'Node': if not node: return None visited = {} def dfs(node): if node in visited: return visited[node] copy = Node(node.val) visited[node] = copy if node.neighbors: copy.neighbors = [dfs(n) for n in node.neighbors] return copy return dfs(node)
question:# Problem Write a Python function that checks if a given string is a palindrome, ignoring case and non-alphanumeric characters. Step 1: Define the function signature The function should take a string as input and return a boolean value indicating whether the string is a palindrome or not. Step 2: Remove non-alphanumeric characters and convert to lowercase We will use a list comprehension to filter out non-alphanumeric characters from the string and convert it to lowercase. Step 3: Compare the string with its reverse We will compare the filtered string with its reverse. If they are the same, the original string is a palindrome. Step 4: Implement the function Here is the Python function that implements the above steps: ```python def is_palindrome(s: str) -> bool: Checks if a given string is a palindrome, ignoring case and non-alphanumeric characters. Args: s (str): The input string. Returns: bool: True if the string is a palindrome, False otherwise. # Remove non-alphanumeric characters and convert to lowercase cleaned_s = ''.join(char.lower() for char in s if char.isalnum()) # Compare the string with its reverse return cleaned_s == cleaned_s[::-1] ``` Step 5: Test the function We will test the function with some examples: ```python print(is_palindrome("A man, a plan, a canal: Panama")) # True print(is_palindrome("Not a palindrome")) # False print(is_palindrome("Was it a car or a cat I saw?
answer:def is_palindrome(s: str) -> bool: Checks if a given string is a palindrome, ignoring case and non-alphanumeric characters. Args: s (str): The input string. Returns: bool: True if the string is a palindrome, False otherwise. # Remove non-alphanumeric characters and convert to lowercase cleaned_s = ''.join(char.lower() for char in s if char.isalnum()) # Compare the string with its reverse return cleaned_s == cleaned_s[::-1]
question:Given a string, find the length of the longest substring without repeating characters. Example 1: Input: "abcabcbb" Output: 3 Explanation: The answer is "abc", with the length of 3. Example 2: Input: "bbbbb" Output: 1 Explanation: The answer is "b", with the length of 1. Example 3: Input: "pwwkew" Output: 3 Explanation: The answer is "wke", with the length of 3. Note: * You may assume the input string contains only of lowercase English letters. Here is a possible solution in Python: ``` def length_of_longest_substring(s): chars = set() max_len = 0 for i in range(len(s)): chars.clear() for j in range(i, len(s)): if s[j] not in chars: chars.add(s[j]) max_len = max(max_len, len(chars)) else: break return max_len ``` However, this solution is not very efficient. Can you provide a better solution with a sliding window approach?
answer:def length_of_longest_substring(s): Returns the length of the longest substring without repeating characters. char_index_map = {} max_length = 0 start = 0 for i, char in enumerate(s): if char in char_index_map and char_index_map[char] >= start: start = char_index_map[char] + 1 char_index_map[char] = i max_length = max(max_length, i - start + 1) return max_length