Update is_palindrome.py

Algorithm optimised in terms of space from O(n) to O(1)

Author: abhishekmulik

strings/is_palindrome.py

@@ -16,7 +16,20 @@ def is_palindrome(s: str) -> bool:
     # Since punctuation, capitalization, and spaces are often ignored while checking
     # palindromes, we first remove them from our string.
     s = "".join(character for character in s.lower() if character.isalnum())
-    return s == s[::-1]
+    # return s == s[::-1] the slicing method uses extra spaces, we can do better with iteration method.
+    
+    end=len(s)//2
+    n=len(s)
+    
+    #We need to traverse till half of the length of string
+    #as we can get access of the i'th last element from i'th index. 
+    #eg: [0,1,2,3,4,5] => 4th index can be accessed with the help of 1st index (i==n-i-1) 
+    #where n is length of string
+    
+    for i in range(end):
+        if s[i]!=s[n-i-1]:
+            return False
+    return True 
 
 
 if __name__ == "__main__":