leetcode 125:Valid Palindrome

原题：

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.

题意为给定一个字符串，判断是否是回文串。只考虑字母或数字，并忽略大小写。

Java实现：

public class Solution {
public boolean isPalindrome(String s) {
int i=0;
int j=s.length()-1;
String str = s.toLowerCase();
while(i<=j){
if(!Character.isDigit(str.charAt(i)) && !Character.isLetter(str.charAt(i)) ) {
i++;
continue;
}
if(!Character.isDigit(str.charAt(j)) && !Character.isLetter(str.charAt(j)) ) {
j--;
continue;
}
if(str.charAt(i)!=str.charAt(j)) return false;
else {
i++;
j--;
}
}
return true;
}
}