【Leetcode】Valid Palindrome

题目链接：https://leetcode.com/problems/valid-palindrome/

题目：

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.

算法：

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1. public boolean isDecent(char c) {
2. if (Character.isAlphabetic(c) || Character.isDigit(c)) {
3. return true;
4. } else
5. return false;
6. }
7. public boolean isPalindrome(String s) {
8. char c[] = s.toLowerCase().toCharArray();
9. int i = 0, j = c.length - 1;
10. while (i < j) {
11. if (isDecent(c[i]) && isDecent(c[j])) {
12. if (c[i] == c[j]) {
13. i++;
14. j--;
15. } else {
16. return false;
17. }
18. }
19. if (!isDecent(c[i])) {
20. i++;
21. }
22. if (!isDecent(c[j])) {
23. j--;
24. }
25. }
26. return true;
27. }