from the error I met
"a" return true
"1a2" return false
I am confused about what is the rule for palindrome for this question
Here is a statement in problem description:
considering only alphanumeric characters
So, numbers and alphabet are counted.
a is 1 character string, it should be a palindrome.
1a2, since digits should be counted, obviously
1 is not
2, the result should be false.