LeetCode OJ：Valid Palindrome（验证回文）

Valid Palindrome

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.

验证回文与否，这个估计大家学c语言的时候就都写过：

 1 class Solution {
 2 public:
 3     bool isPalindrome(string s) {
 4         int len = s.length();
 5         for(int i = 0, j = len - 1; i < j ;++i, --j){
 6             while(i < j && (!isalpha(s[i]) && !isdigit(s[i])))
 7                 i++;
 8             while(j > i && (!isalpha(s[j]) && !isdigit(s[j])))
 9                 j--;
10             if(isalpha(s[i]) && isalpha(s[j])){
11                 if(toupper(s[i]) == toupper(s[j]))
12                     continue;
13                 else return false;
14             }else{
15                 if(s[i] == s[j])
16                     continue;
17                 return false;
18             }
19         }
20         return true;
21     }
22 };

java版本的代码如下所示，算法没有变化：

public class Solution {
    public boolean isPalindrome(String s) {
         int sz = s.length();
         int beg = 0, end = sz - 1;
         while(beg < end){
             while(!Character.isLetter(s.charAt(beg)) && !Character.isDigit(s.charAt(beg))){
                 if(beg < end) beg++;
                 else return true;
             }
             while(!Character.isLetter(s.charAt(end)) && !Character.isDigit(s.charAt(end))){
                 if(beg < end) end--;
                 else return true;
             }
             if(Character.toUpperCase(s.charAt(beg)) == Character.toUpperCase(s.charAt(end))){
                 beg++;
                 end--;
             }else{
                 return false;
             }
         }
         return true;   
    }
}