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.

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.

思路:

将原字符串去掉非字母和数字,全部转化为小写,在判断回文

代码:

 1     bool isPalindrome(string s) {
 2         // Start typing your C/C++ solution below
 3         // DO NOT write int main() function
 4         string t = "";
 5         for (int i = 0; i < s.length(); i++) {
 6             if (s[i] >= 'a' && s[i] <= 'z' || s[i] >= '0' && s[i] <= '9' || s[i] >= 'A' && s[i] <= 'Z') {
 7                 if (s[i] >= 'A' && s[i] <= 'Z') {
 8                     t += (s[i] - 'A' + 'a');
 9                 }
10                 else {
11                     t += s[i];                    
12                 }
13             }
14         }
15         if (t == "") {
16             return true;
17         }
18         for (int i = 0; i < t.length() / 2; i++) {
19             if (t[i] != t[t.length() - i - 1]) {
20                 return false;
21             }
22         }
23         return true;
24     }

 

posted on 2013-11-04 22:56  waruzhi  阅读(132)  评论(0编辑  收藏  举报

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