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.
分析
题目给出一个字符串，判断该字符串是不是回文，但是要忽略除了数字字母以外的任何字符，并且不区分大小写，而且有空字符串的情况出现，空字符串判定为真
解题的想法就是，先得到干净的字符串（只有字母数字），然后首位开始依次向中间移动开始判断
代码
class Solution {
public:
bool isPalindrome(string s) {
//判断字符串是不是为空，为空直接true
if(s.empty())
return true;
//去除除了字母和数字以外的所有字符
string str = clear(s);
for (int i=0,j=str.length()-1;i<j;i++,j--){
if (str[i]!=str[j]){
return false;
}
}
return true;
}
//清理函数，将字符串去除除了字母和数字意外的字符，并将全部字符转为小写
string clear(string s){
string str = "";
char c;
for(int i=0;i<s.length();i++){
c = s[i];
if (c>='A'&&c<='Z' || c>='a'&&c<='z' || c>='0'&&c<='9'){
if (c>='A'&c<='Z')
str+=c+32;
else
str+=c;
}
}
return str;
}
};
