18.验证回文串
方法:双指针
class Solution {
public boolean isPalindrome(String s) {
int l = 0,r = s.length() -1;
while(l < r){
while(l < r && !Character.isLetterOrDigit(s.charAt(l))){
l++;
}
while(l < r && !Character.isLetterOrDigit(s.charAt(r))){
r--;
}
if(l < r){
if(Character.toLowerCase(s.charAt(l)) != Character.toLowerCase(s.charAt(r))){
return false;
}
l++;
r--;
}
}
return true;
}
}