题目描述：
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.
判断回文。需要跳过特殊字符以及同一个字母大小写视为相等的情况。
实现代码：public class Solution {
public bool IsPalindrome(string s)
{
var i = 0;
var j = s.Length - 1;
while(i < j){
while(Skip(s[i]) && i < j){
i++;
}
while(Skip(s[j]) && i < j){
j--;
}
var delta = s[i] - s[j];
if(delta != 0 && delta != 32 && delta != -32){
return false;
}
i++;
j--;
}
return true;
}
public bool Skip(char c)
{
var a = (int)'a';
var A = (int)'A';
var z = (int)'z';
var Z = (int)'Z';
var v = (int)c;
var zero = (int)'0';
var nine = (int)'9';
if(v >= a && v <= z || v >= A && v <= Z || v >= zero && v <= nine){
return false;
}
return true;
}
}