Merge and add benchmarks to palindrome algorithms in the strings/ directory (#8749)

* refactor: Merge and add benchmarks to palindrome

* updating DIRECTORY.md

* chore: Fix failing tests

* Update strings/palindrome.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update palindrome.py

---------

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
Co-authored-by: Christian Clauss <cclauss@me.com>

DIRECTORY.md

@@ -1156,7 +1156,6 @@
   * [Indian Phone Validator](strings/indian_phone_validator.py)
   * [Is Contains Unique Chars](strings/is_contains_unique_chars.py)
   * [Is Isogram](strings/is_isogram.py)
-  * [Is Palindrome](strings/is_palindrome.py)
   * [Is Pangram](strings/is_pangram.py)
   * [Is Spain National Id](strings/is_spain_national_id.py)
   * [Is Srilankan Phone Number](strings/is_srilankan_phone_number.py)

strings/is_palindrome.py

@@ -1,41 +0,0 @@
-def is_palindrome(s: str) -> bool:
-    """
-    Determine if the string s is a palindrome.
-
-    >>> is_palindrome("A man, A plan, A canal -- Panama!")
-    True
-    >>> is_palindrome("Hello")
-    False
-    >>> is_palindrome("Able was I ere I saw Elba")
-    True
-    >>> is_palindrome("racecar")
-    True
-    >>> is_palindrome("Mr. Owl ate my metal worm?")
-    True
-    """
-    # 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] the slicing method
-    # uses extra spaces we can
-    # 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
-
-    return all(s[i] == s[n - i - 1] for i in range(end))
-
-
-if __name__ == "__main__":
-    s = input("Please enter a string to see if it is a palindrome: ")
-    if is_palindrome(s):
-        print(f"'{s}' is a palindrome.")
-    else:
-        print(f"'{s}' is not a palindrome.")

strings/palindrome.py

@@ -1,5 +1,7 @@
 # Algorithms to determine if a string is palindrome
 
+from timeit import timeit
+
 test_data = {
     "MALAYALAM": True,
     "String": False,
@@ -33,6 +35,25 @@ def is_palindrome(s: str) -> bool:
     return True
 
 
+def is_palindrome_traversal(s: str) -> bool:
+    """
+    Return True if s is a palindrome otherwise return False.
+
+    >>> all(is_palindrome_traversal(key) is value for key, value in test_data.items())
+    True
+    """
+    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
+    return all(s[i] == s[n - i - 1] for i in range(end))
+
+
 def is_palindrome_recursive(s: str) -> bool:
     """
     Return True if s is a palindrome otherwise return False.
@@ -40,7 +61,7 @@ def is_palindrome_recursive(s: str) -> bool:
     >>> all(is_palindrome_recursive(key) is value for key, value in test_data.items())
     True
     """
-    if len(s) <= 1:
+    if len(s) <= 2:
         return True
     if s[0] == s[len(s) - 1]:
         return is_palindrome_recursive(s[1:-1])
@@ -58,9 +79,26 @@ def is_palindrome_slice(s: str) -> bool:
     return s == s[::-1]
 
 
+def benchmark_function(name: str) -> None:
+    stmt = f"all({name}(key) is value for key, value in test_data.items())"
+    setup = f"from __main__ import test_data, {name}"
+    number = 500000
+    result = timeit(stmt=stmt, setup=setup, number=number)
+    print(f"{name:<35} finished {number:,} runs in {result:.5f} seconds")
+
+
 if __name__ == "__main__":
     for key, value in test_data.items():
         assert is_palindrome(key) is is_palindrome_recursive(key)
         assert is_palindrome(key) is is_palindrome_slice(key)
         print(f"{key:21} {value}")
     print("a man a plan a canal panama")
+
+    # finished 500,000 runs in 0.46793 seconds
+    benchmark_function("is_palindrome_slice")
+    # finished 500,000 runs in 0.85234 seconds
+    benchmark_function("is_palindrome")
+    # finished 500,000 runs in 1.32028 seconds
+    benchmark_function("is_palindrome_recursive")
+    # finished 500,000 runs in 2.08679 seconds
+    benchmark_function("is_palindrome_traversal")