added two pointer directory and added solution to is_palindrome

Author: Daanish-Hindustani

data_structures/two_pointer/__init__.py

@@ -0,0 +1,100 @@
+"""
+Problem Overview:
+
+Is Palindrome - Easy - Spotify
+
+Given a string s, return true if it is a palindrome, otherwise return false.
+
+A palindrome is a string that reads the same forward and backward.
+It is also case-insensitive and ignores all non-alphanumeric characters.
+
+Example 1:
+
+Input: s = "Was it a car or a cat I saw?"
+
+Output: true
+Explanation: After considering only alphanumerical characters
+we have "wasitacaroracatisaw", which is a palindrome.
+
+Example 2:
+
+Input: s = "tab a cat"
+
+Output: false
+Explanation: "tabacat" is not a palindrome.
+
+Constraints:
+
+1 <= s.length <= 1000
+s is made up of only printable ASCII characters.
+
+"""
+
+
+class Solution:
+    def is_palindrome(self, s: str) -> bool:
+        """
+        This method checks whether the input string `s` is a palindrome or not.
+        It ignores non-alphanumeric characters and is case-insensitive.
+
+        Parameters:
+        s (str): The input string to check.
+
+        Returns:
+        bool: True if the string is a palindrome, False otherwise.
+
+        >>> Solution().is_palindrome("Was it a car or a cat I saw?")
+        True
+        >>> Solution().is_palindrome("tab a cat")
+        False
+        >>> Solution().is_palindrome("")
+        True
+        >>> Solution().is_palindrome("A")
+        True
+        """
+
+        """
+        Initialize two pointers, left (l) at the start, and right (r) at
+        the end of the string.
+        """
+        left, right = 0, len(s) - 1
+
+        while left < right:
+            # Skip non-alphanumeric characters from the left pointer.
+            while left < right and not self.is_alpha_numeric(s[left]):
+                left += 1
+            # Skip non-alphanumeric characters from the right pointer.
+            while left < right and not self.is_alpha_numeric(s[right]):
+                right -= 1
+
+            # Compare characters at both pointers in a case-insensitive way.
+            if s[left].lower() != s[right].lower():
+                return False
+
+            # Move both pointers towards the center.
+            left, right = left + 1, right - 1
+
+        # If all characters match, it is a palindrome.
+        return True
+
+    def is_alpha_numeric(self, c: str) -> bool:
+        """
+        Helper function to check if a character is alphanumeric (A-Z, a-z, 0-9).
+
+        Parameters:
+        c (str): The character to check.
+
+        Returns:
+        bool: True if the character is alphanumeric, False otherwise.
+        """
+        return (
+            ord("A") <= ord(c) <= ord("Z")
+            or ord("a") <= ord(c) <= ord("z")
+            or ord("0") <= ord(c) <= ord("9")
+        )
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()