Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.
For example,"A is a palindrome.
man, a plan, a canal: Panama""race is not a palindrome.
a car"
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.
去掉S中的无关字符，将大写字母转换为小写，之后就是简单的回文串判断。
- class Solution {
- public:
- bool isPalindrome(string s) {
- // Start typing your C/C++ solution below
- // DO NOT write int main() function
- string t = "";
- for (int i = 0; i < s.length(); i++) {
- if (s[i] >= 'a' && s[i] <= 'z' || s[i] >= '0' && s[i] <= '9' || s[i] >= 'A' && s[i] <= 'Z') {
- if (s[i] >= 'A' && s[i] <= 'Z') {
- t += (s[i] - 'A' + 'a');
- }
- else {
- t += s[i];
- }
- }
- }
- if (t == "") {
- return true;
- }
- for (int i = 0; i < t.length() / 2; i++) {
- if (t[i] != t[t.length() - i - 1]) {
- return false;
- }
- }
- return true;
- }
- };