#	ref: Zybooks Chapter 7.9 Lab: Palindrome

#  simple is_palindrome. Case sensitive, not removing any characters.
def is_palindrome_1(s):
    """ Algorithm
       if s == reverse of s:
           return True
       else:
           return False

    if s == s[::-1]:
        return True
    else:
        return False
    """
    return s == s[::-1]

#   using an alternative method.
def is_palindrome_2(s):
    """ return s == reverse of s
    """
    return s == "".join(list(reversed(s)))
    
def is_palindrome_3(s):
    #   case insensitive
    """ s to convertdc to lower case == reverse of s converted to lower case
    """
    return s.lower() == s[::-1].lower()

def remove_non_aphabet_chars(s):
    """ [1] whether a char is an alphabet.  char.isalpha
        [2] remove those that are not alphabet.
        Algorithm:
        [1] result = ''
        [2] loop through char in s:
                if char is alphabet:
                    result = result + char
        [3] return result
        
    """
    result = ''
    for char in s:
        if char.isalpha():
            result += char
    return result

def is_palindrome_4(s):
    #   case insensitive and remove non-alphabetic characters.
    """  [1] t <- remove non-alphabetic characters of s.
         [2] t.lower() == t[::-1].lower()
    """
    t = remove_non_aphabet_chars(s)
    return t.lower() == t[::-1].lower()
    
s1 = "racecar"
s2 = "Racecar"
s3 = "Hello world"
s4 = "A Toyota's a Toyota."
print(f"s1: {s1}")
print(f"s2: {s2}")
print(f"s3: {s3}")
print(f"s4: {s4}")


print(f"is_palindrome_1(s1): {is_palindrome_1(s1)}")
print(f"is_palindrome_1(s2): {is_palindrome_1(s2)}")
print(f"is_palindrome_1(s3): {is_palindrome_1(s3)}")
print(f"is_palindrome_1(s4): {is_palindrome_1(s4)}")

print(f"is_palindrome_2(s1): {is_palindrome_2(s1)}")
print(f"is_palindrome_2(s2): {is_palindrome_2(s2)}")
print(f"is_palindrome_2(s3): {is_palindrome_2(s3)}")
print(f"is_palindrome_2(s4): {is_palindrome_2(s4)}")

print(f"is_palindrome_3(s1): {is_palindrome_3(s1)}")
print(f"is_palindrome_3(s2): {is_palindrome_3(s2)}")
print(f"is_palindrome_3(s3): {is_palindrome_3(s3)}")
print(f"is_palindrome_3(s4): {is_palindrome_3(s4)}")    

print(f"is_palindrome_4(s1): {is_palindrome_4(s1)}")
print(f"is_palindrome_4(s2): {is_palindrome_4(s2)}")
print(f"is_palindrome_4(s3): {is_palindrome_4(s3)}")
print(f"is_palindrome_4(s4): {is_palindrome_4(s4)}")