Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.
For example,"A man, a plan, a canal: Panama" is a palindrome."race a car" is not a palindrome.
Note:
Have you consider that the string might be empty? This is a good question to ask during an interview.
For the purpose of this problem, we define empty string as valid palindrome.
题解：这道题比较简单。
class Solution {
public:
char strLwr(char c)
{
if(c-'A'>=0 && c-'A'<=26)
{
return 'a'+c-'A';
}
return c;
}
bool isAlphanumeric(char c)
{
if(c-'0'>=0 && c-'0'<=9)
{
return true;
}
if (c-'a'>=0 && c-'a'<=26)
{
return true;
}
if (c-'A'>=0 && c-'A' <= 26)
{
return true;
}
return false;
}
bool isPalindrome(string s) {
int len = s.length();
string ss = "";
int i;
for(i=0; i<len; ++i)
{
if(isAlphanumeric(s[i]))
{
ss += strLwr(s[i]);
}
}
string rss(ss.rbegin(), ss.rend());
if (ss == rss)
{
return true;
}
return false;
}
};