Python/other/palindrome.py
percy07 1ed47ad6f4 Update palindrome.py (#1509)
* Update palindrome.py

Add Doctests.

* Use test_data to drive the testing
2019-10-29 11:22:49 +01:00

67 lines
1.6 KiB
Python

# Algorithms to determine if a string is palindrome
test_data = {
"MALAYALAM": True,
"String": False,
"rotor": True,
"level": True,
"A": True,
"BB": True,
"ABC": False,
"amanaplanacanalpanama": True, # "a man a plan a canal panama"
}
# Ensure our test data is valid
assert all((key == key[::-1]) is value for key, value in test_data.items())
def is_palindrome(s: str) -> bool:
"""
Return True if s is a palindrome otherwise return False.
>>> all(is_palindrome(key) is value for key, value in test_data.items())
True
"""
start_i = 0
end_i = len(s) - 1
while start_i < end_i:
if s[start_i] == s[end_i]:
start_i += 1
end_i -= 1
else:
return False
return True
def is_palindrome_recursive(s: str) -> bool:
"""
Return True if s is a palindrome otherwise return False.
>>> all(is_palindrome_recursive(key) is value for key, value in test_data.items())
True
"""
if len(s) <= 1:
return True
if s[0] == s[len(s) - 1]:
return is_palindrome_recursive(s[1:-1])
else:
return False
def is_palindrome_slice(s: str) -> bool:
"""
Return True if s is a palindrome otherwise return False.
>>> all(is_palindrome_slice(key) is value for key, value in test_data.items())
True
"""
return s == s[::-1]
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")