Problem

Given a singly linked list, determine if it is a palindrome.
Example input: 
1->2->2->1
Example output: 
true

Solution

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            //create a linked list
            LinkedList<int> list = new LinkedList<int>();
            list.AddFirst(1);
            list.AddLast(2);
            list.AddLast(2);
            list.AddLast(1);

            //create a stack
            Stack<int> stack = new Stack<int>();

            //push the first half of the linked list into the stack
            int count = 0;
            foreach (int i in list)
            {
                if (count < list.Count / 2)
                {
                    stack.Push(i);
                }
                count++;
            }

            //pop the stack and compare the popped value to the second half of the linked list
            //if the values are not equal, then the linked list is not a palindrome //if the values are equal, then the linked list is a palindrome
            count = 0;
            foreach (int i in list)
            {
                if (count >= list.Count / 2)
                {
                    if (stack.Pop() != i)
                    {
                        Console.WriteLine("false");
                        break;
                    }
                }
                count++;
            }
            Console.WriteLine("true");
        }
    }
}