一. integer 和 character 之間轉換
//one integer is 12321, pick up every digit one by one
int x = 12321;
int n1 = x; //after remove digits from right side
int n2 = x; //after remove digits from left side
for(var i = 1;i <= l/2; i++)
{
var p = Math.Pow(10, digits-i);
int x1 = n1 % 10; //the digit will be removed from right side
int x2 = (int) (n2 / p); //the digit will be removed from right side
if(x1 != x2) return false;
n1 /= 10;
n2 -= (int)(x2 * p);
}
return true;