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.
其中可以在以后刷题中用到的：
Character.isLetterOrDigit()
Character.toLowerCase()
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public class {
public boolean isPalindrome(String s) {
if(s==null)
return true;
int len=s.length();
int p=0;
int q=len-1;
while(p<q)
{
while(Character.isLetterOrDigit(s.charAt(p))==false&&p<q)
{
p++;
}
while(Character.isLetterOrDigit(s.charAt(q))==false&&p<q)
{
q--;
}
if(Character.toLowerCase(s.charAt(p))!=Character.toLowerCase(s.charAt(q)))
{
return false;
}
else
{
p++;
q--;
}
}
return true;
}
}
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