public class Solution {    Stack
     
       S = new Stack
      
       ();        Queue
       
         Q = new Queue
        
         ();        public bool IsPalindrome(string s)        {            if (s.Length == 0)            {                return true;            }            s = s.ToLower();            foreach (var c in s)            {                if ((c >= 'a' && c <= 'z') || (c >= '0' && c <= '9'))                {                    S.Push(c);                    Q.Enqueue(c);                }            }            while (S.Count > 0)            {                var ss = S.Pop();                var qq = Q.Dequeue();                if (ss != qq)                {                    return false;                }            }            return true;        }}