Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.
Note: For the purpose of this problem, we define empty string as valid palindrome.< /p>
Example 1:
Input: "A man, a plan, a canal: Panama"
Output: true
Example 2:
Input: "race a car"
Output: false
class Solution(object):
def isPalindrome(self, s):
"""
:type s: str
:rtype: bool
"""
if s is '':
return True
import string
valid = set(string.ascii_letters + string.digits)
s_cp = s[:].lower()
left, right = 0, len(s)-1
while left <= right:
if s_cp[left] not in valid:
left += 1
elif s_cp[right] not in valid:
right -= 1
elif s_cp[left] != s_cp[right]:
return False
else:
left += 1
right -= 1
return True
class Solution(object):
def isPalindrome(self, s):
"""
:type s: str
:rtype: bool
"""
if s is '':
return True
import string
valid = set(string.ascii_letters + string.digits)
s_cp = s[:].lower()
left, right = 0, len(s)-1
while left <= right:
if s_cp[left] not in valid:
left += 1
elif s_cp[right] not in valid:
right -= 1
elif s_cp[left] != s_cp[right]:
return False
else:
left += 1
right -= 1
return True