#
# @lc app=leetcode.cn id=125 lang=python3
#
# [125] 验证回文串
#

# @lc code=start
class Solution:
    def isPalindrome(self, s: str) -> bool:
        tp_rtn = True
        first_ptr = 0
        last_ptr = len(s) - 1
        while (first_ptr < last_ptr):
            frt_str = s[first_ptr]
            lst_str = s[last_ptr]
            # filter none ascii str
            while not frt_str.isalnum():
                first_ptr = first_ptr + 1
                frt_str = s[first_ptr]
                # break loop
                if first_ptr >= last_ptr:
                    break
            while not lst_str.isalnum():
                last_ptr = last_ptr - 1
                lst_str = s[last_ptr]
                # break loop
                if first_ptr >= last_ptr:
                    break
            # Judge whether first str equal last str
            if (frt_str.isalnum() and lst_str.isalnum()):
                if frt_str.lower() != lst_str.lower():
                    # Not valid str
                    tp_rtn = False
                    break
            first_ptr = first_ptr + 1
            last_ptr = last_ptr - 1
        # Return result
        return tp_rtn
# @lc code=end

test_str = '0P'
tp_func = Solution()
print(tp_func.isPalindrome(test_str))